I recently stumbled on a fantastic web application called SmartyTask. It's extremely intuitive and quick to use. I've read David Allen's Getting Things Done book (a fantastic read by the way) and this software makes it easy for me to apply the principles taught in the book.
My favorite feature is the ability to have a general inbox, and drag-and drop items to different contexts. I created a context for every one of my coworkers (e.g. a John, Jason, Nikki, etc.). When there's something I think of that I need to discuss with them or delegate to them, I drag my inbox item to their context and it's instantly on my list.
I then carry my fancy Xoom tablet around the office with SmartyTask open and check of the items that get done as I speak with my coworkers. For a good productivity system, I recommend SmartyTask. They have a 7 day free trial too.