Great question, Michele!
There are so many! I am looking forward very much to Bill Whitaker's workshop this spring, to start.
I have been fortunate to have studied with a number of wonderful painters, and I'd absolutely recommend:
Burt Silverman
Dan Gerhartz
Harley Brown
I've also learned a tremendous amount from Phil Beck, who teaches at the Scottsdale Artists School.
In addition to the many of the SOG artists Michele mentions, others - who may not be as familiar to the folks here - I'd really like to study with include:
Robert Johnson
Kim English (Wow! I think he is one of the best when it comes to composition)
Sherrie McGraw
Mary Massey
Scott Christensen
Allan Banks, too
I am extrememly interested in filling some gaps I have in still life, landscape and composition.
Ah, so much to learn, so many zip codes.