Superseded by new release:
I've just posted a beta of PNotes Portable (as suggested by Have Some Patience). PNotes is a sticky note utility that allows you to post sticky notes on your screen. It has multiple display options as well as a handy feature to schedule notes to pop up. It's small (under 1MB) and works well on Windows 2000 and up. Please give it a try and post your feedback.
Please post any feedback.