Lars Trieloff ponders upon a context-aware to-do-list system Actually, dividing tasks into contexts so that each task can be dealt with when you're at the best time and place for it is a basic principle in David Allens Getting Things Done
I've been practising the GTD approach for some time now and it helps me in a great way to keep focus on what has to be done, when it has to be done and where I can do it.
I use Backpack!.html to manage my task lists. Every context (at home, at work, places i can use a phone, etc.) has its own page with a to-do-list there. Every task finished gets ticked off, and the next day, I delete (with great pleasure) all these old tasks.
With Tracks, there's even a special software to practise GTD online. I haven't tried it yet, but it looks promising.