7 Sticky Notes is a lightweight and simplistic app that enables you to create sticky notes directly on your desktop. More info in here:
This tool can also be installed as a portable product. It means that you can store it on a removable drive, save it to any computer and directly run its executable file. More importantly, the Windows registry is not altered in any way. Customization options revolve around the font (e.g. style, size, emphasis, alignment, color), style (e.g. transparency level, note theme) and alarms.