DC COMICS HEROES!!!!
(...and in 2007 - MARVEL Heroes!)
Dig em! I like that its a mix from the different Comic Eras; Golden Age, Silver Age, Modern Age...
This added with the MUPPETS stamps, the U.S. is finally starting to have some cool stamps for us dorky citizens! Before, we had to geek on foreign stamps like Mongolia's X-MEN or the REPUBLIQUE TOGOLAISE's super sweet ALIEN stamps (which I have, thanks to ebay. heheh)