Windows only: Freeware application Anti Keylogger Shield blocks keyloggers from tracking the passwords and other personal information you type on your computer.
Unlike other similar tools, Anti Keylogger Shield does not detect existing keylogger software; it just disables the mechanisms they use to record your typing.
While I can’t vouch for this app across the board, I did install one keylogger and it worked as advertised—I typed, but the log remained empty.
This would be a real winner if it were portable and could run from thumb drives.

Anti Keylogger Shield [via Red Ferret]