This was announced on TiVoCommunity.com today. From the project Wiki page:

TiVo.Net is a windows service that acts as a TiVo GoBack server. It loads many standard video compression codecs and outputs mpeg2 video to the TiVo. It allows you to watch videos that are stored on your computer in, say, DivX format without having to wait for the video to be transcoded first. On the low quality settings(1024kBit video, 128kBit audio), my computer has no problem sending the video faster than the TiVo can play it.

This is an open source project hosted on SourceForge and it uses FFMPEG to do the transcoding, so it should theoretically handle any video format that FFMPEG handles. It installs and runs as a Windows service. It is written in C#, so if anyone wants to get it working under Mono on Linux, or port it to other platforms, feel free.

Note that this is a VERY early release, the current version is 0.2.1a at the time of this posting, so this is really beta level software right now. If you run it, be prepared to experience bugs and provide feedback to the developer. But it does look like a nice application already, with some features TiVo Desktop’s TiVoToComeBack functionality could really use. And it does transcoding, which is a promised feature for the forthcoming Desktop Plus 2.4 – though this likely supports more video formats and provides more control to the user.

Check it out if you want to play with something.