Here's the free way to do it.
http://www.engadget.com/2005/10/18/how-to-get-tv-s...

After reading all the steps involved with this approach, I opted to spend $25. And while the transfer process of transfering a show from your tivo to your computer is painfully slow... I tend to move the shows off my tivo to my computer while I sleep.

The upside is you can set it to automatically create portable versions whenever you transfer shows to your computer. So when I wake up in the morning, all my iPod files are ready to by synch'd.