This week, I received a question that my home video / prosumer side enjoys: "What software should I use for converting [name of video format here] to Windows Media Video files?"
At home, I use TMPGEnc 3.0 XPress and Riverpast's VideoCleaner for doing transcodes between a variety of different formats. They're both excellent products, and I like TMPGEnc as it has good editing and video correction utilities built in. A popular option for professional video conversion is Autodesk Cleaner XL (which I think used to be Media Cleaner Pro).
A good resource for doing conversions, video formats and tools, I really like the http://www.videohelp.com/ site. It's well organized and has links to just about every piece of video software out there.