VisualHub

I love VisualHub. It's a cheap (not free) video converter that just works. It converts just about anything to anything, even .flv and .wmv.

Features:
Fast conversion from nearly every video format to iPod, PSP, DV, DVD, Tivo, AVI, MP4, WMV, MPEG and Flash.
Convert any file in three steps. Click, drag, click.
Fit up to 18 hours of video on one DVD. Play it in any standalone DVD player.
Xgrid support. Use the power of every Mac on your network for batch encoding.
QuickTime Pro or special plugins not required.
DivX/XviD AVIs, all forms of MPEG video, and many other formats QuickTime struggles with are supported.
Batch Processing of multiple files. Save in-place, or to a different folder.
Very comprehensive Advanced panel to modify every aspect of encoding.
Dynamic Preview - See results before beginning a long encode.
Stitch multiple files together to combine videos.
Highly detailed, informative Users Guide.
Universal Binary for PowerPC and Intel Macs.

Give it a try.