Pedro has a new item in at United Armory, the Jin Roh Waist Armor. Made of soft plastic this part moves with your minifig.
The item can be painted to match any armored concept you might be working on. (EDIT: As Jas points out in the comments, these flexible parts don't take paint well. Apologies for the confusion.) Given my recent fascination with Halo, I could see this complimenting a SPARTAN in sand green.
If you are in the US or Canada, you can visit United Armory on BrickLink to pick up a few of your own.
(Via Pedro's Flickr stream)