A shared address book system where members lists of contacts set up a global people network that helps you keep in touch with old friends. (Google)
Twitter is a free service that lets you keep in touch with people through the exchange of quick, frequent answers to one simple question: What are you doing? (Google)
As you requested at the end of the last training, you wanted a forum space to keep in touch with one another, swap ideas, share photos/documents etc. So here is your space! (Google)