Seems like you want some GTD (Getting Things Done) software. Apart from reading the book (by David Allen), which I encourage you to do, you should probably use this:
http://whatsnextapp.com
I think it will suit you well, and it's the most no-brainer interface I found, that can really follow the GTD method.
Trimpath (Google Gears) also seems pretty interesting. I personally ended up buying Things, and I have to say, it paid for itself already, and is worth all the hype that it gets. It's Mac only, unfortunately.