I've been working on an autonomous sail boat for about 18 months. I've got something that works, but needs a lot of tuning:

https://www.youtube.com/watch?v=AUwbx9gO6aA

It's a bit smarter than in that video, but still gets lost when crossing wind:

I've got everything up on Github: https://github.com/kolosy/ArduSailor

Would love any feedback or input!