Also: https://developer.betfair.com/ http://forum.bdp.betfair.com/

I was careful about using someone else's code for handling my money! So I used basic example code that I understood (I no longer remember where I got it, sorry), then extended it.

From various forums etc, there seems to be a big pool of people doing this sort of thing. Also, from the betting market dynamics, you can see there are other algo traders - watching the in-play betting on soccer matches is quite amazing - the bettors work with such small margins and big volumes, 'predicting' the game in real-time. Most impressive.