At the moment, not much - Apple's displays and some third-party external drives. There are announced plans from Sony and Asus (I think) to add it to their laptops toward the end of the year, and Intel is close to adding support to their chipsets. I'm interested to see if Apple's approach (partnering with Intel) will help it avoid Firewire's fate.
Compare: http://blekko.com/ws/c%23+get+custom+attribute+/monte
With: http://www.google.com/#hl=en&q=c%23+get+custom+attribute
Blekko claims the first google result is "C: Summary for Citigroup, Inc. Common Stock- Yahoo! Finance", while google finds the relevant information.