I'm working on a Tivoweb module to take iCal files and convert them. You could use your Tivo as a server for ics files with this, or just broadcast a specific schedule as an RSS feed that could be piped back to your TV or another computer. Specifically, I use this to view my work schedule on my TV. It's still in beta; the big feature on the todo list is web access for the iCal files. Download it at http://davidlauria.com/software.
Please post any comments or questions in this thread.