I have our house monitored by cameras and run a package called Active Webcam to record it and broadcast it on the web. I use some cheap Airlink 101 Ethernet cameras as well as some Toshiba Pan/Tilt/Zoom cameras outdoors:

http://www.toshibasecurity.com/produ...il_ikwb15a.jsp

To be honest, the cheapest solution at the moment is probably an outdoor floodlight/camera solution I've seen at Costco for $100. This thing has a motion sensing floodlight AND a built in camera that records to an SD memory card. Nice and simple, but will require you to hook it up to power.