TheoraEncoders

theora: reference encoder/decoder (the decoder support all theora features) library with MMX optimizations: theora svn, theora official releases.
theora-old: old encoder/decoder (the decoder does not support all theora features, but it's faster than theora in many cases) library, with MMX optimizations; theora version up to 1.0 alpha 7 were using this code trunk: theora-old svn.
theora-exp: experimental encoder/decoder (the decoder is more or less the same of reference, the encoder is new and supports all theora features but it's not really usable) library: theora-exp svn.
theora-thusnelda: another experimental encoder; it should be more usable than theora-exp and should replace the reference encoder in the future (the decoder is the same of reference), library: theora-thusnelda svn. For more info sees here: Theora "the push for 1.0" update and Theora: The push for 1.0, Thusnelda project update 20080320.
theora-multithread: experimental encoder based on the reference encoder optimized for SMP/multi core systems: theora-multithread svn. For more info sees all the thread here: Multi-Thread Theora Encoder.
Etheora: a simplified API to theora reference encoder/decoder.

See also