Motion capture is a special animation technique that allows human actors to define the movements of an animated character. Special cameras track the actor's movements and can then transfer them onto a CG character. The result is a simple yet realistic method of animating. Unfortunately, however, motion capture systems are very expensive, far too expensive for the hobbyist. That's where this great resource comes in!
There are numerous sites which contain free motion capture data for many major 3D programs, but none specifically cater to Blender. Thankfully, though, the "feeblemind" Blender blog has created a nice little tutorial on how to use certain motion capture animations inside Blender. The tutorial also gives links to multiple sites where motion capture can be downloaded for free. You still may not be able to do your own motion capture, but mocap becomes affordable, this is the next-best thing. Don't miss it!