Motion Capture ("MoCap")

Idea: Do not create keyframes and curves manually, but let the computer record live action, possibly performed by a trained actor
Most kinds of motion capture technologies can also be used for real-time control: "computer puppetry"
Technology:

Markers = retro-reflective balls. Example: Vicon
Current research: use only one camera and/or no markers
RF transmitters of RF receivers attached to the actor's body. Example: Polhemus
Plused light, possibly infrared. Example: P5 data glove (position and orientation of the hand)
Exoskeleton [Außenskelett]. Examples: P5 data glove (bending of the fingers), Gypsy
Ultrasound
Accelerometers, Gyroscopes. Example: head tracker
Computer mouse, graphics tablet, etc.
Convert audio recordings to animated mouth shapes. Example: Caligari trueSpace

Some examples for professional-quality face-tracking
Stundent's project: "Latah" face-tracker
Standard file format for animated skeletons: Biovision BVH; now superseeded by the much more general Kaydara FBX

Non-Linear Animation

Idea: Use partial animations like video clips in non-linear video editing [nichtlinearer Videoschnitt] such as Adobe Premiere and Apple Final Cut. Construct animations from simple or not-so-simple "clips" that can be shifted and copied to different instances of time, that can be layered (motion mixing) and blended using transitions (motion blending). These clips do not contain pixel data but movements.
Demo
Non-linear animation facilitates editing motion capture data with its tons of keyframes.