I have a few Superman toys/figures only. My favorite being the Target Exclusive The World's Greatest Hero Clark Kent to Superman figure. This one is cool as it is a 2-in-1 figure. You get Clark Kent (who else) and Superman. And it comes with a phone booth for quick change action!
Ebay selling at USD30-50 range.
Another favorite is the Silver Age Superman and Lois Lane figure. I got this many years ago while on a trip to Singapore. The figures have good articulation and you can put them in two beautiful pose, a standing on a base with American flag and also Superman carrying Lois flying pose. My next favorite is the Superman Doomsday boxed set that comes with the Death of Superman comic book. I got it at reasonable price in Borders. Produced by DC Direct, you can expect the kind of articulation from DC Direct figures. Comes with two S logo bases.
Ebay selling (Silver Age set) USD 40, (Supes & Doomsday set) USD 25.
Other Supes figures I have are from the Animated line, the recent Movie line and also some kid stuff. Funny, Superman figures don't go up in value as quickly compared to Batman figures though its one of the first (or is it the first?) superheroes created.