I also have the WD TV and it could play the latest codecs, so it's a good choice. You can plug in up to two USB devices simultaneously. I usually plug in an 8 GB thumb drive or a 1 TB disk drive. WD TV also has the live edition that you can connect to your home router and directly play clips from Youtube and other online video streaming sites.

Among the other good yet inexpensive ones I've seen are media streaming products from Xtreamer, Buffalo, Asus, and Seagate. Other brands that carry media streaming products are Popcorn, Boxee, Zyxel, Syabas, Roku, and Netgear, among others.