Security Camera setup

[Jonathan Hutchins]

I have a friend who's getting unauthorized "visits" from her deadbat ex.  I'd 
like to set up a security camera that will capture the images of anybody who 
comes and goes when she's not home.  I know that there are PC Cameras and 
software packages that will use the camera as a motion detector and variously 
post images to a web page or at least start recording.  Is anyone familiar 
with these things?

Is there a package that will do this in Linux, and if so, what hardware do I 
need?