Discovering WEB 2.0 tools

I'm picking google docs as a tool that I really like and think is useful. This allows someone to produce and access documents from anywhere they are and then even post them to their blog. All of this without even buying any software or installing it on their machine. For the library this is useful as many of our clients don't own a computer so prior to tools like this they could not even create document or spreadsheet and then save it for future use.