There are some free ones out there and some can be pretty good. Tmpgenc
http://www.tmpgenc.net/ is one of them but it can be a little hard to use for the uninitiated. It is also limited as far as formats is concerned. A very inexpensive program that I bought a while back and use quite often despite having some powerfull video editing programs is AVS Media Converter
http://www.avsmedia.com/
Right now only $24.95 and it's great. Very good quality, will make any size output you want, and will handle most of the major formats and cross convert. Give it a look, I highly recomend it.