I just bought ProxyLeech.com.
Unfortunately, it's built using VB.net. This means I'll have to find some Windows hosting until I get this recoded to work under Unix.
It's a pretty interesting little site. It focuses on port proxies, which is quite different than my usual focus on web proxies. (Terminology gets a little clumsy here...)
Proxies currently have to be added manually, but they are checked automatically.
Is there an off-the-shelf script with similar functionality, or will I need to have something custom coded?
Not really sure. I've never really seen anything like it. Cool little site. How much did it cost? :)
Could just scrap known sites and store the content via text until the internal system can check them and if they are good it would post them. Think it would be easier then running scanning scripts 24/7 to find use able ip proxies. Then again if you can find your own and can get script created that use a lot of resources then there is damn good money to be made selling access to them.