Here is a picture of an activity I did with my 6th graders during my student teaching.  I felt it was necessary to help build a more positive classroom community and help build up each student's self esteem.  I called it "Hearts of Gratitude" - each student was required to write the name of each of their classmate's name on one side of a heart and then on the other a compliment or positive note to the classmate.

Here is a close up of a group of hearts and you can see just a simple note of saying Hi can go a long ways to building camaraderie within the classroom environment, though I stopped just putting Hi on the hearts quickly.

I definitely think I will incorporate this activity next year, but possibly sooner; possibly Christmas, and instead of hearts I will have the students write on stars.