International Super Teams are us.
This gives you the basics for a setting for a super powered game in the GURPS system. Now, GURPS is a bit brutal for your four colour type superhero adventures, so keep that in mind when you use it. You are thinking Wildstorm or that sort of thing here, really.
3 out of 5
The above link is the complete list of post from this blog, updated each week, if you want to browse like that rather than search.
This list is quite long, and has become longer than I ever thought so in the interests of loading speed it is now situated elsewhere.
Similarly I am working on a simple website to browse by author that combines Free SF Reader and Not Free SF Reader that is extremely bare bones now, and can be found at the second URL above.