http://lifehacker.com/software/lifehacker-top-10/top-10-free-video-rippers-encoders-and-converters-316478.php

1. Handbrake (Open source/Windows, Mac) - Back up your DVD's to digital file with this open source DVD to MPEG-4 converter app. http://handbrake.m0k.org/
2. DVD Shrink (Freeware/Windows only) - Copy a DVD to your hard drive and leave off all the extras like bonus footage, trailers and other extras to save space with DVD Shrink. http://www.dvdshrink.org/
3. VidDownloader (webapp) - When you don't want to mess with installing software to grab that priceless YouTube clip before it gets yanked, head over to web site VidDownloader which sucks in videos from all the big streaming sites (YouTube, Google Video, iFilm, Blip.TV, DailyMotion, etc.), converts 'em for you to a playable format and offers them for download. Other downloaders for online video sites buy you a Flash FLV file, but VidDownloader spits back an AVI file. http://www.viddownloader.com/
4. Any Video Converter (Freeware/Windows only) - Convert almost all video formats including DivX, XviD, MOV, rm, rmvb, MPEG, VOB, DVD, WMV, AVI to MPEG-4 movie format for iPod/PSP or other portable video device. http://www.any-video-converter.com/products/for_video_free/
5. Avi2Dvd (Freeware/Windows) - Make your video files burnable to a DVD with Avi2Dvd. http://www.trustfm.net/divx/SoftwareAvi2Dvd.html
6. MediaCoder (Open source/Windows) - Batch convert audio and video compression formats. http://www.rarewares.org/mediacoder/