GovDeals is like eBay for surplus or decommissioned equipment. I've seen some good deals on there before for electronics so I browse it occasionally. The upside is cheap equipment. The downside is that you don't really know the quality of what you're getting, and sometimes they won't ship it and you have to pick it up locally. Today I found these listings:

20 Outdoor Cameras in South Carolina (bid starting at $50):

Four elevator cameras in Arkansas (bid is at $100)

A bunch of dash cams and light bars in North Carolina (bid is at $30)

A 7-camera bus surveillance system with a VHS recorder (bid is at $1, the listing says a premium bid is $10)