One of the striking things about the Google offices is that there are whiteboards everywhere. Googlers stand around these board to collaborate, brainstorm, problem solve...
As you are planning your classroom and considering putting up another version of the same old bulletin board consider instead covering your walls with whiteboard. What problems might you and your students solve if every surface (or even one wall) in your classroom was writable? At a cost around $10.00 for 25 square feet it is a cheap price to pay for allowing unlimited collaboration.
You can buy it many places including; Amazon and iKorDesign. Have fun!