Quick Notes Plus
After installing the QNP trial, my Windows firewall blocked the program. Conceptworld addresses this situation in a FAQ on their site. I unblocked it, but if that makes you uncomfortable, and you don't plan to send your sticky notes over a network, they suggest you right-click on the QNP icon in the system tray, then choose Advanced, Work Offline from the context menu. That should eliminate the security alerts.
A revamped, expanded, and friendlier version of this program, called NoteZilla, is available for $30. Though it lacks some of the features of NoteZilla, QNP is still pretty robust. Both programs are available at a discount if you are buying more than one license.