So I've put together a very simple application that demonstrates serial communication with the OBDPro interface. It is written in .NET and commented throughout.
http://www.digitaldeviation.com/projects/obd2
Like I said, its a simple. I may add more to it later (there's a lot to add to a full fledged app). Hopefully it will help someone get started though. This should work with the ELM327 as well.
I'm working on a full app myself, but I thought I'd toss out something to help out.