While many people are familiar with track-changes in MS Word, there are other options for collaborative writing and editing. 37 Signals - makers of the excellent (and free) Backpack personal organizer - have applied similar AJAX scripts to create a free, web-based writing software that feels like a desktop program.
What does this mean for the scholar? Now you have an easy way to enlist your peers to help you review your projects. For example, let's say you have a writing group - each class member can log on to Writeboard and make their edits. Afterwards you can compare and accept the useful changes. Or what if you are working on group paper? Now you can easily track previous versions and edits.
Plus, you can't beat the price.