Microsoft Office Live
I have been a long time user of Google Docs keeping my graduate school documents on it for some time. I think Microsoft has hit a massive home run with Office Live. The migration of Microsoft in to a web based Live product has been slow and painful, but Live just a better site than Google Docs. The primary problem is the Live is Microsoft centric still and I can't use it on my Linux machines using Flock browser, but for an XP based machine the integration between Microsoft Office Live and Office 2003 and 2007 makes it a no brainer. The site is also easier to use and provide more pre-existing business templates.