More news has been revealed om the upcoming maps for Halo 3:
http://xbox360.ign.com/articles/101/1013150p1.html
For those of you who don't know this map pack will contain 3 new maps and, as far as we know, will only be shipped out with Halo 3: ODST. This article also contains some news on the extremely awesome looking Firefight, the GoW2 Horde but for Halo.
Personally, out of the new maps coming out, Longshore is getting me pretty excited, finally a map that you can play some good ol' Tower of Power.