I'm largely self-taught, but I've found inspiration and good instruction from several artists along the way. If you're an artist, please check these sites for useful painting tips and techniques.
If you're not an artist, check their sites anyway to see examples of their beautiful work.
Dan Edmondson - Dan is my current teacher. I'm working with his still life DVD set. I'm having great fun and learning a lot, too. I hope to complete his landscape course next.
Paul Taggart - Paul has posted more useful painting videos than anyone else I know. He has videos for all mediums, too. I learned the concept of surface mixing from him - mixing one's paint on the canvas rather than on one's palette.
Thomas Baker - Tom taught me that one can improve by trying to copy the works of the Old Masters. Even if you do a poor job, you'll still get better fast.