Risa and Elusion at livejournal.com created a wonderful MAC reference site, located at http://www.legacycollection.org/
Here, you can find almost every shade of anything MAC has created, all of the face charts, brushes, bags, media, polishes, etc. This is great when you want to reference certain items and see just what MAC has come out with. Let's also not forget www.specktra.net, with an awesome forum, news about future collections, and other great info. Also, www.macpro.com has all those great products that you just can't order on the regular site.