For something a bit lighter, I've just read in Jason Rosenhouse's Evolutionblog that Spider-Man 3 will feature Sandman as its supervillain.
As a kid, I rated this character (who is not to be confused with the totally different character created by Neil Gaiman) among my favourite villains. He can turn his body to sand, or to solid rock, or a mixture, can take any shape, packs a helluva punch in his rocky form, and cannot be hurt by any amount of force (enough force can break rock, but he can just turn to sand and reform). There's scope here for some great special effects if it's done right.
I'm not such a huge fan of the Spider-Man movies - can pretty much take them or leave them - but this one might be a lot of fun.