Wallwisher - collaborate with an online virtual sticky note maker. Incorporate text, audio, links and video.
Corkboardme - a lot like Wallwisher. No login or account needed. Very easy to share.
Today's Meet -my favorite back channel (chat room). Completely private and simple to start. My students beg me to use this tool.
Typewithme - a lot like Google Docs. Easy to set up and share. Create in real time.
Skype - collaborate with others across the country and world through video conferencing. My students really want their own Skype accounts.
Do you have a favorite tool for collaboration with your students? Please share with all of us.