One of the best things about Halo 3 is the Forge mode, but it can be a pain in the warthog to create a new map from scratch each time you get an idea.
That's why one player has gone through all of the trouble for you. Chevmeister has created blank map variants and shared them on Bungie.net.
Players can download these blank slates and get right to the editing. Hit the cut for links to each variant.
Remember, if you log into your Bungie.net account and have your gamertag linked, you can set these maps to download the next time you boot up Halo 3.
Here is the original forum post: clicky!