Titan Pad is a great web tool for educators. It provides a free collaborative workspace for users. It is based on EtherPad set up to enable users to work on their documents in real time. This is similar to Type with Me that I have covered earlier. These collaborative tools do not require any sign up and they are ready to use as soons as you are on their homepage.
Just head over to Titan Pad and click on create a Public Pad. Once created you can then share the URL of this pad wth your friends and people you want work with. There is also a chat window to talk to your colleagues while working on documents.
I do recommend this tool to teachers and students. It is really great.
Watch this video tutorial to learn more