Windows 96 – This is the fanciest web OS I could find. It has PC games in it, a software repository, and its own Linux emulator. Pretty nifty stuff! It is still in active development, so the developer is always adding new stuff.
Windows 93 – This one is very similar to Windows 96. I don’t think it is in active development anymore, but it is still fun to play with.
Virtual x86 – This is ACTUALLY an operating system in your browser. You can choose Windows, Linux, BSD, and others to run in a virtual machine on your browser. Just click the OS you want and run it. Cool stuff!
Cyberspace and Time – This one is kind of a mess. It still has cool games and tools, but it isn’t my favorite because the UI is messy. Still, this person worked hard on it for 20 years so go check it out.