Here's another online application that I discovered on The Collaborative Web pagecast. It's a writing tool that can be used individually and/or with others to collaborate on any type of writing project. Writeboard saves every version of a document so that one can easily view and compare different versions. You can subscribe to writeboards via RSS so that you'll always know of any changes made by others. Another neat feature is that Writeboard integrates with Backpack.
If you have a Backpack account you can attach writeboards to backpack pages or see a list of all your writeboards in one place on the Writeboards tab from within Backpack. You can also create new writeboards in Backpack. Using Backpack and Writeboard together is a great way to keep your writing organized (and not have to remember multiple usernames and passwords).
I'm all for having fewer logins to remember, so making use of both these online applications makes great sense to me.