For me, it is essential to keep to-do lists simple. I use business card-size note cards. They are a handy size, easy to sort, and easy to throw away.
I have tried the Palm Pilot, computer outlines, etc. None of them have helped me.
The most difficult part about work is getting organized. Doing the work is easy. We've had plenty of practice at doing our various tasks. We're masters at what we do. Deciding what to do next is the difficult part about work.