BOLL's Multiplayer Emblem Generator
Halo 2 allows you to customize an emblem for your uniform while playing multiplayer - BOLL's provided you with an interface for building an emblem for use on the web, or just for experimenting with the options. If you want to use one of these as your avatar on, say, the HBO Clan forum, simply set the size to 90 px or smaller, copy the URL into a new window, then save the resultant image to your hard drive, so that you can upload it to a server somewhere. If you want to save a work in progress, but you're not sure if you're done, simply copy the URL in the 'Editor' field at the bottom; it will get you back to exactly where you left off.
Thanks to Bungie for allowing us to use their bandwidth for this!