I've spoken to many individual and business users of Google Docs & Spreadsheets and there are definite themes in how people are using the product.
Timesheets are often mentioned.
Roto Meier has some ideas in this space and wrote a great post about it in his blog .
He also seems to have become very resourceful with the Google APIs and written a whole Timesheets application which he makes available online.
When I get a chance to actually install his tool and try it, I'll write more about it.