I have been using Google Docs all all my loose documents because I can access them everywhere with internet connection. During lunch time, I work on my sermons on Google Docs, and go home to continue my preparation. Besides word documents, the spreadsheets are especially useful to keep track of church information (e.g. outreach RSVPs, church directory) that needs to be shared among selected people. All these involve a browser only and no need to have word/excel installed on the PC and worry about copying files, synch up, etc.
Recently Google Docs add the support to create powerpoint presentation and this is pretty cool. I am sure in the future I would be able to find use of it.
IMHO, few application on the web are as sticky as google’s offerings. Its calendar too is indispensable to me and my ministry. The Picasa and its web albums, the google maps, google/youtube video, and more… all are good for integration. And all with a goal to drive people to sign up google.