[SIZE="5"]Avalanche[/SIZE]


It's a "spiritual" remake of Sidewinder from the original Halo. So, I'm assuming spiritual means, "It's snowy and in a canyon." Kind of how Guardian is a "spiritual" remake of Lockout. Small and in the air.
[SIZE="5"]Blackout[/SIZE]


Now, as I've already stated, Guardian is a "spiritual" remake of Lockout. This, however, is a REAL remake of Lockout, and all I can say is... Well, nothing. EXCEPT HOLY SHIT! Lockout was my favorite map on Halo 2 and I can't wait to see how it works out with Halo 3's gameplay.
[SIZE="5"]Ghost Town[/SIZE]


Not really anyway to describe this one. It's not really modeled after an older map. It's a map you'd have to play to see what it's like. It personally reminds me of Overgrown on CoD4.
These are the new maps coming out.
Also, the Heroic Map Pack [Rat's Nest, Foundry, and Standoff] is now free to download in the Xbox Live Marketplace.