The BYU Museum of Art is perfect for any visit, whether you plan to delve deep into 150 years of American painting at their permanent exhibit, or just want a quick run through one of their visiting shows. Entry is free, and the museum is small, so it's great for a quick browse (between classes if you're a student) but not so small that you ever feel like you have seen everything, because the BYU Museum of Art is constantly changing exhibits and otherwise updating itself.
If possibly, try to make it there during lunch so you can treat yourself to a bite to eat at the MOA cafe. Tasty, trendy food at an affordable price. Also, don't miss out on the museum gift shop which is always good for a decent poke around. I've never known anyone to not like this museum.