PopChar - The character map that works!
Free Virtual Keyboard - Free Virtual Keyboard is a free, lightweight, multilingual and finger friendly virtual keyboard.
WinCompose - WinCompose supports the standard Compose file format.
Hot Virtual Keyboard - A replacement for Windows' built in virtual touch keyboard.
Holdkey - Holdkey is a Windows program that makes it easy to type characters with accents..
AllChars - If you're new to AllChars: start with the Introduction, see the FAQ and Manual. And finally download it. AllChars is now Open Source, usage is free and the sourcecode is available.