We like this a lot.
The website superherostuff.com, offers a selection of super hero t-shirts that are not your average tee: Superman, Batman, Robin, Joker and other characters are available for boys.
Our favorite, the costume caped t-shirts, simulate the outfit of the super hero, such as Superman's cape (see the pictures above).
Girls will find a nice selection of tees including a few with cape: Batgirl, Super Girl and Wonder Woman.
Go check it out!