http://ourinstantwin.com/ - A very good site, kept up to date regularly. This is my favorite site to use for IWGs.
http://snazzywin.com/instants.html - This is also a nice site, I use it as a back-up on the rare occasion that ourinstantwin goes down. In my opinion, it's not as nicely organized as ourinstantwin.
http://itsallfreeonline.com/instant-win-game-roundup/ - Yet another nice list of IWGs. It is apparently kept up to date very well. I don't like the way it is organized, but it's a nice alternative.
