There's an increasing buzz about Hydra, a collaborative writing tool for Mac OS X that allows people to share a document and then edit it simultaneously over the Internet or local networks. Hydra's uniqueness is in the live editing: you can see other people's insertion points and selections, and use a following function to track someone's editing as they type.In a daisy chain this morning, I discovered Steve Gillmor linking to Clay Shirky who links to Bill Bumgarner's description of using Hydra at Apple's Worldwide Developer's Conference (WWDC) a few weeks ago. The organizers of the show had set up Hydra templates to allow participants to make notes on the talk and to queue up questions! Good gravy. My co-author Adam Engst on The Wireless Networking Starter Kit and I just spent a couple of hours using iChat AV (audio only) and Hydra to rework the outline for the book. We easily saved 50 percent of the time by both being able to take notes and point out items to each other simultaneously in a long text stream. Reading aloud and working separately on documents just isn't as efficient.