Working in real-time with EtherPad
Before Google Wave washes away (hah!) the competition in September, it’s worth noting (hah!) EtherPad where you can already collaborate in real-time on a text editor.
A simple idea and very well executed with up to eight people editing at any one time. Personally the Author enjoys choosing which colour he likes to highlight in but is assured there are better uses to which it could be put.