Here is an example of a professional Facebook page that I enjoy, plus it's not the typical corperate-advertisement-crazy type of page.
Lonesome Road
I tend to stay away from “liking” any company, band, person, or anything else for that matter. “Liking” tends to spam up my mini-feed and overall create a great amount of annoyance. However, I have chosen to “like” Lonesome Road, which is a country band that mostly plays in small-town bars in eastern Iowa. The band (or whoever updates the page) does a very good job of posting upcoming shows, thanking the audience for attending, and other fun tidbits throughout the week. The tones of the postings are fun, informative, and exciting.