If you have an old web cam or two laying around you can convert them into a CCTV system that pushes email and growl notifications to you any time motion is detected in the area they are monitoring.
Sean, a DIYer from the UK, wanted to put his always-on-server to even more use. By linking a webcam to the server and setting up Yawcam (for the motion detection and email notification) on the server and a growl/prowl server (for the push notifications to desktops and iOS devices). So far his setup has worked perfectly, his next project is to build a more weather-proof enclosure (rather than a simple piece of flashing to keep direct rain off, as we see in the photo above).
Hit up the link below to read more about his project and setup an emailing/growling security cam of your own.