WinCompose – A Compose Key for Windows
I'm a big fan of the compose key, both for its universality and intuitive "syntax". For many years I endured the pain of a dual French/US keyboard layout (one for writing, the other for coding), until a coworker showed me the special Option-key shortcuts you can use on a Mac to make French accents, and then finally I settled on the nice and intuitive Compose Key support offered natively by Ubuntu: https://help.ubuntu.com/community/ComposeKey