One possibility suggested last week which I like is:

> **[How do I set PATH and other environment variables?](http://superuser.com/questions/284342/how-do-i-set-path-and-other-environment-variables)**
> 
> Explains Environment Variables for
> different Operating Systems in a
> quick, dense, info-packed package.
> (You don't have to go through an
> entire 10-page article learning how
> they work; just learn the relevant
> stuff here.)