You can go check out the options for the stamps (and vote for your favorite, for another few weeks) here. Apparently the Leia and R2-D2 stamp is getting a lot of votes. I think I'd like the Han Solo one more if it were a better likeness of Harrison Ford. ;)
In the meantime, they have created R2-D2 mailboxes and placed 400 them around the country. (I have yet to see one, but maybe they've posted a location list someplace...) So you knew this was going to happen. Classic!
What I really want is one of those mailboxes. How many of them do you think will get stolen? (yes, it's a Federal offense, but really... people are stupid, and we all know how nutty Star Wars fans are!)
Oh, and incidentally, postage rates are going up again this month! Better go out now and buy some 2-centers (Mom, this means you!) because it's gonna be 41-cents as of May 14th.