You can make yourself a HipsterPDA. Or just have a plain notepad. Having that with yourself is also beneficial for capturing ideas. The only thing that beats paper here, for me, is a one-or-two-clicks voice note recorder in your phone.

Or if you go everywhere with a backpack, you can carry a thin paper binder with your task list with you. I've once used to do both binder and HipsterPDA at the same time.

//EDIT

> I use taskwarrior. It's CL and kicks ass. http://taskwarrior.org

I thought by 'CL' you mean 'Common Lisp' and went straight to downloading the application source. It's not Lisp, it's 'Command Line' :(. Anyway, the app looks really nice.

Command Line = CLI, Common Lisp = CL. I was wondering why being written in Common Lisp made it good.

For me it was more a matter of personal curiosity, since you don't really see much Lisp applications around.