Recently I've had success incorporating collaborative vocabulary activities into my American History lessons using Todaysmeet.com, a chat-based website purposed for educational backchanneling. Take a look at this recent chat window from my class:
I've found Todaymeet works wonders as a bellringer, as it really helps students settle in and begin focusing on an integral part of a particular day's lesson. The power of this website goes far beyond using it for vocabulary. Formost, it can be used as a power backchanneling tool for students to collaborate and share opinions and knowledge with each other as they learning. The best part about this website is how easy it is to implement. Students need not sign up for an account, as they simply type in the webaddress for their teacher's Todaysmeet room.