GTD 2.0

David Allen's book, Getting Things Done, has a cult following, including software devs that try to make tools for GTD. Emily has a list of them here.

Allen’s Getting Things Done describes five stages of mastering workflow: collect, process, organize, review, do. [emily] “The goal of GTD is [to] get things as much off your mind as possible..."

Google Notebook, Jott, Remember the Milk, Backpack, 30boxes, Nozbe, Vitalist, SimpleGTD, and others