Free GM Resource: Classic Marvel Forever
The folks over at Classic Marvel Forever have done what they can to maintain a long-since dead RPG. While their site does have links to downloads of what appears to be the entire non-supported Marvel Super Heroes RPG line, I think you'll find a slew of other resources as well.
Now I'm sure that these downloads violate common-sense intellectual property rights, but I personally don't get to worked up about abandoned properties. If Ha$bro manages to pick up the rights to d a re-print of this game or Di$ney does one themselves, please let me know and I'll delete this post right-quick.*
If these companies don't care enough about the game to make it available to those who want to play, then they don't care enough about these product being available for download. If I'm just plain wrong about this, please feel free to let me know. I've had a few required courses on copyright and trademark law but I've also had a few life lessons on the law vs. reality.
*OK, I'll admit using the dollar signs might be a bit much....