In general, a fully functional hand doesn't exist for the hobby market. The hands on the market that aren't two-fingered, pinch style grippers typically run in the many thousands of dollars range (I think that the Barrett Hand, a fairly common one, is somewhere around $11K). This is due to the unfortunate fact that hands are really, really hard to build and control. Now that being said, it's not impossible to build one -- I'm currently building one with three fingers, two links per finger, fully articulated at each joint, and controlled by an axon. We have the first finger built and I'm doing control trials with it.
Since the topic comes up a lot here, I'm probably going to post the design. It uses parts from solarbotics and an Axon for control, so it's not all that expensive (we're probably going to come in at around $400 CDN) but hands aren't cheap!
I'll keep you all posted once the hand itself gets built. something tells me we're going to have some troubles along the way :-P