i love post-its! you could decoupage them on a table (either one color, coordinating colors, or go really bright and have a neon multicolored table!) i don't know if i explained that well, but it looks really cool in my head....
or you could decouage them all over....
a purse (it would be really colorful and wouldn't match much-except any shirt that matched the color of one of the post its-but it would be really neat looking)
anything basically........you could easly stick them in place then paint glue over them (clear glue!) or something like PuzzleSaver (the clear stuff that keeps puzzles together that you want to use as artwork or w/e- you could get it at Michael's or other craft stores) or something like that....
this may have been totally confusing but again in my mind it sounds really easy and i think it would come out looking really nice
sorry the pics are so small!