I recently got my hands on a great book by Scott Belsky - Making Ideas Happen, the first chapter of which is devoted to the topic of getting organized. Scott's proposal is simple -- each major idea that you want to move forward should be treated as a project. Each project in turn should have:
1) action steps (tasks that need to be completed)
2) references (any information related to a project), and
3) backburners (brilliant ideas that you want to come back to later, but are not yet actionable).

While reading it occurred to me that Remember the Milk easily allows to implement this approach. For example, for my small entrepreneurial endeavor:
- I create a new list (project),
- add what and when I have to accomplish (action steps),
- capture new ideas that come to mind as tasks with no due date (backburners)
- and store additional information either directly in tasks' notes or in online tools such as Evernote (references). E.g. specifying the following URL for a task gives me direct access from RTM to all Evernote documents that I have collected in the course of my project:

https://www.evernote.com/Home.action#x=tag:myproject

With all the relevant information in one place I stay focused on execution, step by step, but also keep the big picture in mind.