My favorite science productivity apps--google docs

This is my favorite word processing app right now and is in fact what I'm writing this post on.  You can generate word processing documents, spreadsheets and presentations in this suite of products.  The best part is that you can collaborate with people by giving permission to others to view and edit your document.
Key features:
1. Work on the same document simultaneously with colleagues
2. Access your documents from any computer
3. Edit your documents offline using google gears
Science use case:
I have found collaborating on manuscripts in this way much more satisfying and efficient than passing 30-40 drafts back and forth between folks.  Getting real time feedback from collaborators is not only a faster way to work, but I think it also results in a better end product.