I have spent the day in the company of a gaggle of Mac users (is 'gaggle' the correct collective term ?). They made me quite jealous with Hydra a collaborative editing tool in which users not only share documents but can work on them simultaneously. It makes things like collective to-do lists or meeting minutes really easy.
So far I haven't been able to find anything similar for my collection of Windows/Linux boxes.
At last! An excuse to by a Mac !