We've often posted about commercial games that have been released into the wild by their publishers. We've found out about them from other blogs, gaming sites, forums and various other places. Here's a handy site called Liberated Games that catalogues these games as they are released and provides links to them. It's a one stop, free game shop. Yay!
There are many notable games there including the Cinemaware series (Wings!), the early GTAs, Descent (1 & 2) Hexen and lots more.