Something else I should talk about sometime is Google Wave. As a product, it failed and deserved to, and I can talk about why that happened without risking defo. As a *project* tho? Wave was a huge success and much of what you use today is based on things that was initially in Wave.
At the bare minimum, multiple people editing a document and seeing the edits each are doing in real time? Wave. Commenting/suggested edits? Wave.
Real time spelling suggestions? Again, Wave. Go back and watch the Google IO video which was the launch of Wave. And all of this was so far ahead of what was the state of the art at the time.