The main system that records and plays videos is by MythTV. The drivers for the Hauppauge cards are written by the Ivtv project. Those drivers still have some issues, but work well for being reverse engineered.
I use Matt Zimmerman's debian package repository.
Even though these people will never read my web site, I want to give my thanks for all their efforts.
The first place you should look is at the main MythTV documents. I read them several times before I even bought my hardware. As you will see, my system is a bit overkill in performance. But if it didn't work out, I was going to make it my desktop system, so I thought might as well make it a nice system. :-)
Another nice guide is Dennis Lou's Debian and a blank hard drive guide. If you are using Hauppauge receivers, skip the whole section about using xawtv to test the recievers. Xawtv doesn't work with MPEG-2 encoding receivers.
Although I used Debian, Jarod's site is an excellent resource for various settings.
Although it wasn't directly helpful, the Linux HTPC HOWTO provides a nice overview.