I've implemented a loose Getting Things Done (GTD) method of task management, and it really is helping me keep my life in order. These days it makes sense to use our technology for GTD and there's a plethora of options to help you do that.
All the cool Mac users swoon over Omnifocus. Omnifocus sure seems great, although a bit pricey and complicated (neither of which I mind very much). The biggest issue I have with Omnifocus, however, is the fact that it's Mac and iOS only. I try to spend as much time as I can in the Apple universe, but for a big chunk of my day I'm using a PC and Android phone for work.
After trying a few apps I settled on Doit.im. I like the fact that it has apps for all the major mobile platforms and it has a nice web app for me to use in the office. From a GTD perspective is has all the things I need. I can quickly capture tasks, assign them to contexts, group them into projects, and create reminders and alerts. I can even create tasks by forwarding important emails to Doit.im.
There are definitely fuller-featured apps out there, but this one is scratching my itch.