I Would Like To Set Up A Home Network Security System, Any Suggestions?

I would like to install up to four cameras, connected to my home network. Has anybody put together a cheap DIY surveillance system in their houses? What did you do?
A few specifics:
- I would like to be able to record up to 24 hours of mid to high quality color video.
- I would like motion detection to trigger recording, and send an email alert.
- I have a few spare computers I can dedicate to monitoring/recording.
- Wireless would be great, but I can easily run my own ethernet cables, or rca cables.
- Sound is not necessary.
- I can set up complicated systems with no problem if it means saving a few bucks by not getting a fancy all-inclusive surveillance system.
- The ability to watch cameras remotely would be nice.
- I currently have a Linksys N wireless router.