ATnotes is a freeware sticky notes application for your Windows desktop.
The notes are just like Post-it's stuck to your monitor, except you can put clickable links to files or web pages in these Post-it's, or set an alarm to pop up a note at a certain time (like a time-senstive call or meeting reminder). You can put these Post-it's into folders, search 'em by keyword, shrink 'em to show only the first line of text, make 'em whatever color you'd like, and send 'em to other computers on the network.
Neat for Post-its fans, but beware of creating an information black hole lined with sticky notes. You know, stuff goes in, and never comes out again.