Andrew Grumet's got a screenshot of his TiVo displaying RSS feeds on his TV, using a hack for TiVo Control Station. Without the capability to grab the item description and read it, I don't know how useful it is, but it's an interesting hack and probably a direction that a someday super TiVo digital home media hub might go.
In TiVo Hacks, a similar hack lets you check an email account and display subject lines and from addresses. That would seem more useful than RSS (especially if you got new mail saying "From:Boss Subject:Get back to work!"), but both pieces of software wouldn't do much besides remind you when to turn off the TiVo and get back to work on your PC.