I haven't seen this in any of the other threads, so I apologize if this is redundant.

http://www.indoor.flyer.co.uk/probe.htm

This guy made a DIY probe for his mill.

I also saw a link to a web-cam mount for a CNC mill, but I can't find it right now. I'll update this thread as soon as I can find it.

http://www.cnczone.com/forums/showthread.php?t=28308

http://www.brucerayne.com/scanz.html