i remember for a while hughes made directtv TIVO recievers. they had 2 usb ports in the back. unfortunately, those usb ports where never activivated through the hughes firmware...which means you can't use it like a series 2 tivo. with the series 2, you can hook it up to a wireless network via a wireless usb adapter.
there might be hacked firmwares out there on the internet, but i wouldnt know what to do with it nor would i want to try it. there are also adapaters you can buy to convert rca's into something your computer will understand...but thats really tedious and its all real time recording.