Songs in the Classroom

I recently did a few posts about the songs I sing in the classroom for student transitions.  You can read my full post here.  These two songs for lining up and going to the carpet are ones that I use quite often.  I've also been known to break out in song when students aren't paying attention and that gets them pretty quickly.  As a grade level team, we have tried to get together once a week for a half hour to sing songs together as a grade.  The students get to learn songs from all of the teachers.  We try to do some that correlate with our curriculum, but also do some just for fun.  What kinds of songs to you sing around the world in your classrooms?