Here's a little info on the 2012 parade:
Honorary Marshals include singer and actress Marie Osmond; Olympians Benita Fitzgerald Mosley and Kristi Yamaguchi; astronaut Buzz Aldrin; Shintaro Ishihara, Governor of Tokyo; and Ichiro Fujisaki,Ambassador of Japan to the United States. The parade is co-hosted by ABC’s Katie Couric with special correspondent Alex Trebek of Jeopardy and ABC7’s Alison Starling and Leon Harris. Standing room along the Parade route is free and open to the public.
If you can't attend, but would like to contribute to the beautification of Washington D.C. or buy a cherry blossom tree for your own home, check out the Arbor Day Foundation website.