The other day I gave TiVo a little grief for releasing a point release of their Mac desktop client with the only change being it is a Universal app (I was kidding, of course). Well, it would seem that the Mac client has a little hidden gem in it. If you follow these directions you'll see a new pane in the TiVo preferences. This allows you to transfer video from your Mac onto your Tivo for viewing on your TV (this feature is called 'TiVoToComeback'). This is disabled by default in the client, so it probably isn't ready for primetime, but if you're adventurous give it a go.
Thanks to Dave for the pic.