I have been using Remember the Milk for just about as long as it has been around, and it has always been a key part of my GTD systems. It is simply THE best list manager I have ever used - bar none.

3 best things about RTM

1. In the cloud so you can access your lists anywhere, including smartphones and tablets
2. Easy list creation and separation by tags and tabs
3. Phenomenal search capabilities

I have no relation or interest to RTM, but have been a happy user for so long, I just want to make sure that everyone is aware that it is a great option.

Thanks