I've been meaning to put together some links on this topic for a while. I've mentioned Merlin Mann's 43Folders site in passing before, but for those of you new to, or curious about, GTD as a approach to personal productivity, here are a few sites of interest.
• What is GTD?: Straight from David Allen himself.
• 43Folders: All of Merlin Mann's posts by GTD category. Lots of useful information and discussion here. Probably best to start here, then go here.
• The Inbox Makeover: A useful post from Merlin on the specifics of email filtering. Users of Entourage can find some additional inspiration here.
• Productivity Whitepaper: A summary of Patrick Rhone's various hi- and lo-tech approaches to incorporate GTD into his life.
• GTD on a Macintosh: Mac users discuss their approaches on MetaFilter.
• Using Omnioutliner: Additional suggestions from Litwack.org using Mac software and... paper.
• Palm Implementations of GTD: Useful discussions of how to incorporate the approach for those of you with a handheld. Want (or need) something a little more lo-tech? Try the Hipster.