Xbox 360 Halo: Reach Map Packs are available this week for half price.
Halo: Reach - Defiant Map Pack -- 400 MS Points (~$5.00)
Halo: Reach - Noble Map Pack -- 400 MS Points (~$5.00)
Both packs are highly rated and definitely worth a download if you haven't picked them up already.
If you don't have Halo: Reach yet, check it out.