I mix and match. I have an old school paper planner where I jot down important meetings, but sometimes I schedule meetings in my cell phone too just as an extra reminder. I also keep a detailed Excel spreadsheet to list all of my current and upcoming projects, so I know at a glance what I have going on in any given week.
I've always been interested in checking out a PDA, though, and thanks to Rebecca's rave reviews, I'm even more intrigued...*heading off to price PDAs now*...