I've been a fan of David Allen's Getting Things Done since I read the book about 6 months ago. As I also use Gmail, I was interested to see this Firefox extension that seems to incorporate the Getting Things Done (GTD to the cognoscenti) concept into Gmail (or vice versa). I'd also come across this article on using Google Calendar using GTD principles. This evening I spent about an hour fiddling with both of these.
These days, I seem to get "punch-drunk" after using the computer for a couple of hours. My brain stops working, and I notice I'm just jumping from web-page to web-page without really taking anything in.
Anyway, after about a couple of hours of jumping back and forth between different help pages and web-sites, it finally dawned on me that GTDGmail isn't an application of GTD to email, as I'd thought; it's using Gmail to get things done in the GTD way! In other words, instead of helping me to file my existing Gmails according to the GTD principles, it asks me to CREATE emails, and send them to myself, each email being a "task" or "action", and the conversations being the "projects" you're working on.
That didn't seem like such an efficient use of my email-time, and I was starting to feel bored, so I turned to the GTD/Google calendar thing. Again, after playing around with it a bit, it dawned on me that I was basically starting to do exactly the same things as with GTDGmail, but using Google Calendar instead. In other words, I was duplicating a GTD system.
All in all, an evening well-spent! My head's spinning, so I'm off to bed. I do recommend David Allen's GTD book, tho. It's a sweet read, and I'm still using his system (or rather still learning to use it, but not bored or tired yet) 6 months later.