Updated April 15th: The USPS has added a few philatelic products. The new ones are shown in bold:

• 589806, Press Sheet without Die-cut, $35.28, (print quantity 1,000)
• 589808 Press Sheet with Die-cut, $35.28 (print quantity 1,500)
• 589810 Keepsake with Digital Color Postmark, $12.95
• 589816 First-Day Cover (Set of 4), $3.72
• 589817 Joint First-Day Cover, (Set of 2), $5.95
• 589818 Full Pane First-Day Cover, $8.38
• 589819 Cancelled Full Pane, $8.38
• 589821 Digital Color Postmark (Set of 4), $6.56
• 589822 Japan Cancelled Half-Sheet, $5.45
• 589823 Notecards, $16.95
• 589824 Framed Art, $39.95
• 589830 Ceremony Program (random), $6.95
• 589831 Stamp Deck Card, $0.95
• 589832 Stamp Deck Card with Digital Color Post­mark (random), $1.99
• 801211 Japan Half-Sheet, $2.95

Updated April 11th: Photos from the U.S. first day ceremony are here.

Updated April 10th: VSC member Chris Lazaroff attended the first day in Tokyo, and tells us there wasn’t much of a ceremony there. However, there was quite a bit of activity, with many collectors flocking to the main post office for to service FDCs with one of the four postmarkes — only one of which will be available through the U.S. Postal Service’s Cancellation Services.

On the left is Chris servicing his CL Cachets FDCs. He tells The Virtual Stamp Club he got a few strange looks because of the number of covers he had!

This is Chris standing before the post office where the postmarks were available:Updated April 8th: From the USPS:
Stamp Fulfillment Services will be offering a joint FDC set of 2, each cover will have 2 US and 2 Japan matching stamps. We will also offer a Japan Post half sheet of mint stamps, and a Japan Post half sheet with Japan Post FDOI cancellation. These items will be listed shortly on the Postal Store @ https://store.usps.com/store for purchase. The US stamps and products are available for pre-sale now and others are being added as quickly as possible.

SKU / $ / Issue / Description
589804 $5.88 Gifts of Friendship Souvenir Sheet
589816 $3.72 Gifts of Friendship FDC Set of 4
589818 $8.38 Gifts of Friendship Full Pane FDC
589819 $8.38 Gifts of Friendship CNC Full Pane
589821 $6.56 Gifts of Friendship DCP Set of 4
801211 $2.95 Gifts of Friendship Japan Full Pane
589817 $5.95 Gifts of Friendship set/2 2 US & 2 Japan on each Joint Issue
589822 $5.45 Gifts of Friendship Japan  CNC Full Pane

Updated April 4th: It appears FDC servicers and others won’t have to buy an extra 6 Japanese stamps with different designs than the Gifts of Friendship joint issue. From USPS spokesman Mark Saunders:

“We will be offering a Japan Post Sheet of 4 stamps, item 801211 for $2.95; Joint Cover Set of 2 (each cover has 2 US stamps with DCP cancel and 2 Japan Post stamps with Japan Post Pictorial Postmark. We also plan to offer a First Day Cover Cancelled Pane of the Japan Post sheet. I don’t have the item number or price on that one yet. These should be available on the Postal Store within the next week.”

Updated April 1st: Here are the basic Japan Post FDCs for this issue: Here’s a closeup of the Japanese postmark: Updated March 24th: First day ceremony information from the USPS: Two ceremonies
Fri., April 10 at 11 a.m.
Sat. April 11 at 2 p.m.

April 10 – First-Day-of-Issue Stamp Ceremony
Tidal Basin at the Welcome Area Performance Stage (near the Paddle Boats)
1501 Maine Avenue, NW
Washington, DC (event is free and open to the public)

April 11 – Special Dedication Stamp Ceremony
55th Annual Sakura Matsuri – Japanese Street Festival
Pennsylvania Ave. Stage (13th Street on Pennsylvania Avenue, NW
Washington, DC (festival requires a $10 admittance fee for ages 13 and older)

Updated March 20th, from the Postal Bulletin:

On April 10, 2015, in Washington, DC, the U.S. Postal Service® will issue the Gifts of Friendship (Forever® priced at 49 cents) in four designs, in a pressure-sensitive adhe¬sive (PSA) souvenir sheet of 12 stamps (Item 589800). This is a joint issue with Japan Post who will issue their stamps on the same day. The $5.88 Gifts of Friendship souvenir sheet may not be split, and the stamps may not be sold individually.

The stamp will go on sale nationwide April 10, 2015.

The U.S. Postal Service and Japan Post jointly issue Gifts of Friendship, a pane of 12 Forever stamps fea¬turing beautiful images of dogwood and cherry blossom trees. This issuance celebrates the enduring bond between two nations on the centennial of the gift of flowering dog¬wood trees from the United States to Japan in 1915. The left side of the pane features four new stamp designs, two created by the Postal Service™ and two by Japan Post. It also includes two Japanese characters meaning “friend¬ship,” the title of the issuance “Gifts of Friendship,” and a short line of selvage text.

On the right side of the pane are eight additional stamps (four each of the two U.S. designs). The first U.S. stamp showcases the Lincoln Memorial with cherry blossoms in the foreground and the second stamp, the U.S. Capitol Building surrounded by pink and white dogwood trees. The Japanese-designed stamps each feature a prominent building in Tokyo: the National Diet Building framed with cherry blossoms and the clock tower outside the National Diet Building behind a foreground of white dogwoods. Text appears on the back of the stamp pane. Stamp artist Paul Rogers worked with art director and designer William J. Gicker to create the stamps. Gicker and Greg Breeding designed the stamp pane. Junko Kaifuchi illustrated the stamps for Japan Post.

How to Order the First-Day-of-Issue Postmark:
Customers have 60 days to obtain the first-day-of-issue postmark by mail. They may purchase new stamps at their local Post Office, at The Postal Store® website at www.usps.com/shop, or by calling 800-STAMP-24. They should affix the stamps to envelopes of their choice, address the envelopes (to themselves or others), and place them in a larger envelope addressed to:

Gifts of Friendship Stamps
Special Events
PO Box 92282
Washington, DC 20090-2282

After applying the first-day-of-issue postmark, the Postal Service™ will return the envelopes through the mail. There is no charge for the postmark up to a quantity of 50. For more than 50, customers have to pay five cents each. All orders must be postmarked by June 10, 2015.

There are twelve philatelic products for this stamp issue:

• 589806, Press Sheet without Die cut, $35.28, (print quantity 1,000).
• 589808, Press Sheet with Die cut, $35.28, (print quantity 1,500).
• 589810 Keepsake with Digital Color Postmark, $12.95.
• 589816 First-Day Cover (Set of 4), $3.72.
• 589818 Full Pane First-Day Cover, $8.38.
• 589819 Cancelled Full Pane, $8.38.
• 589821 Digital Color Postmark (Set of 4), $6.56.
• 589823 Notecards, $16.95.
• 589824 Framed Art, $39.95.
• 589830 Ceremony Program (random), $6.95.
• 589831 Stamp Deck Card, $0.95.
• 589832 Stamp Deck Card with Digital Color Post¬mark (random), $1.99.

Technical Specifications:

Issue: Gifts of Friendship Stamps
Item Number: 589800
Denomination & Type of Issue: First-Class Mail Forever
Format: Pane of 12 (4 designs)
Series: N/A
Issue Date & City: April 10, 2015, Washington, DC 20066
Designer: William J Gicker, Washington, DC
Art Director: William J Gicker, Washington, DC
Typographer: Greg Breeding, Charlottesville, VA
Artist: Paul Rogers, Pasadena, CA
Modeler: Joseph Sheeran
Manufacturing Process: Offset, Microprint
Printer: Ashton Potter (USA) Ltd. (APU)
Printed at: Williamsville, NY
Press Type: Muller A76
Stamps per Pane: 12
Print Quantity: 80,000,004 million stamps
Paper Type: Nonphosphored Type III, Block Tag applied
Adhesive Type: Pressure-sensitive adhesive
Processed at: Ashton Potter (USA) Ltd. (APU)
Colors: Black, Cyan, Magenta, Yellow
Stamp Orientation: Horizontal
Image Area (w x h): 1.35 x 0.91 in./34.22 x 23.18 mm
Overall Size (w x h): 1.49 x 1.05 in./37.78 x 26.74 mm
Full Pane Size (w x h): 8.50 x 5.25 in./215.90 x 133.35 mm
Press Sheet Size (w x h): 10.63 x 25.75 in./269.88 x 654.05 mm
Plate Size: 144 stamps per revolution
Plate Numbers: N/A
Marginal Markings:
Front: Header: Gifts of Friendship
Back: © 2015 USPS • USPS logo • Barcode (589800) • Promotional text • Verso text

Updated March 16th: Here’s what the entire U.S. pane or souvenir sheet will look like. (We’ll try to replace this with a larger, clearer version.) Updated March 8th: Here are the first-day postmarks for this issue: From the conference call with the USPS on February 20th: April 10th, joint issue with Japan, in Washington, DC, both Dogwood and Cherry Blossom trees (one stamp for each, 2 stamps from each country). Each country will issue the stamps in panes of 12 stamps. The U.S. panes will have 10 of the U.S. designs, plus two of the Japanese design with the U.S. Forever denomination. It will be the reverse on the Japanese panes: 10 of its designs, plus two of the U.S., all with Japanese denominations. Awaiting agreement and designs from Japan, could be as soon as Monday the 23rd. Coincides with the centennial of when President Taft sent the 50 dogwood trees to Japan, in return for the 3,000+ trees Japan sent the U.S. in 1912.

From the USPS:
In 2015, the U.S. Postal Service and Japan Post will jointly issue Gifts of Friendship, a pane of 12 stamps featuring beautiful images of dogwood and cherry blossom trees. There are two stamp designs for each country…one featuring the dogwood and the other featuring the cherry blossom.

The stamp issuance coincides with the Centennial of President William Howard Taft’s gift of dogwood trees to the people of Japan in 1915.

In early 1912, Tokyo gave the city of Washington, D.C., more than 3,000 cherry blossom trees.

As a show of gratitude for this generous gift, former President Taft arranged to have 50 flowering dogwood trees (Cornus florida) sent to Japan in 1915. This reciprocal gift featured a species of tree native to the eastern United States and Canada.

These gestures of goodwill fostered a rich tradition of exchanging cherry blossom and dogwood trees that continues to this day.
Artist: Paul Rogers
Art Director: Bill Gicker

Here’s what the Japan Post issue will look like: According to Japan Post’s website, the four individual stamps on the left will measure 25.0 mm (0.984 inches) by 35.5 mm (1.398 inches). The stamps on the right will measure 28.0 mm (1.102 inches) by 38.5 mm (1.516 inches). The denominations will be 82 yen (currently 68¢ U.S.) The entire sheet will sell for $6.80; no word yet if the USPS will sell just the two Japanese stamps. The two Japanese stamps show Sakura and the Houses of Parliament and Dogwood and Kenseikinenkan Clock Tower.

A Google translation of the Japan Post page is here.