Worship the Glitch (WTG) has a great post about finding free MPEG2 content online to stream to your updated TiVo. The Internet Archive is a huge repository aiming to be the world's library, with the goal of capturing and curating all human knowledge. Part of the Archive is their immense video library, which includes MPEG2 versions of all sorts of public domain, freely licensed, and open source movies.
WTG has offered a useful new service, GlitchTV. It's a daily feed featuring a movie from the Archive. Coupled with some podcasting software mentioned in the post, you could have automated nightly downloads of every movie in the GlitchTV feed delivered to your PC. Then it'd just be a matter of firing up your TiVo each night to see what wacky new movie awaits viewing.