I'm currently having two songs stuck in my head right now, and both of them are really good.
The first song I have trapped within my brain is More Than Words by Extreme. I love the song, it sounds great, has a good message, and I just love the unplugged feel of the song (which is more relevant in the music video).
The second song that I cannot get to escape my ears is The Scare Floor, composed by Randy Newman for the film Monsters, Inc. It has a really nice, gritty, industrial-like jazz feel, and I love Jazz works that do that.