Post-it for computers
As a Mac user I am spoiled. Among many other built-in goodies the Mac has notes. These are screen equivalents of post-it notes. They linger on your screen as reminders until you release them. I use them all the time. Joel Garreau made this suggestion for the majority Windows users.
You know about computer screen stickies? Here’s a little program I’m in love with. Available for free, although it gives you an opportunity to tithe on Paypal.