Canopus has a great A-D/D-A converter called the ADVC100. Read about it here:
It sells for around US$250 and has great features such as locked audio and reverse conversion, meaning you can stream the digital signal off of the computer back onto a VHS or DV tape. You will need to get software such as Pinnacle Studio 8 to do any editing and publishing to DVD or tape. It connects to your computer via Firewire (ieee-1394).