Seems to me that your problem is not making your to-do list more efficient, but actually more effective. Any to-do list system (rememberthemilk, GTD, Outlook, etc...) will help you with the efficiency part, but not with the effectiveness part.

I highly recommend you the book First Things First, by Dr. Covey: http://www.amazon.com/First-Things-Learn-Leave-Legacy/dp/0684802031/