Preferably one that is VCD compliant.
TMPGenc is generally considered the best at this. Click on the name in this post to pull it up in the Tools section here and then click on the direct download link to get it. This version is free.
There also exist: QuEnc, NuEnc, bbmpeg ( which is even slower than TMPGEnc ), and
mpeg2enc ( assuming you're not afraid of the command-line, of course ).