Post-it Digital Notes
You can make to-do lists and reminders, color code your virtual notes, add photos to them, sort them by category, and set reminder alarms. There's even a feature that lets you create virtual corkboards on which you can post your notes, to help you get even more organized.
There's one caveat, however: Post-it Digital Notes requires the Microsoft .Net framework to run. If you don't already have it installed, 3M's installer will download and set it up for you--but it takes a while, even on a broadband connection.