Onboard on-screen keyboard

If you cannot use a physical keyboard, the built-in Windows on-screen keyboard is usually the first thing you find, and often the last one anybody tells you about. Between it and full AAC systems costing thousands, there is a whole category most people never discover. This list collects what is actually out there for typing without a physical keyboard on a desktop computer: free tools, paid ones, and a few built for eye tracking or switch access. I have tried to note who each one is for, because "on-screen keyboard" covers products that solve very different problems. Disclosure: I build one of the products in this space. Everything here is listed on merit, including the ones that compete with mine.