A simple keylogger written in python. It is primarily designed for backup purposes, but can be used as a stealth keylogger, too. It does not raise any trust issues, since it is a set of [relatively] short python scripts that you can easily examine.
LKL is a userspace keylogger that runs under Linux on the x86 arch. LKL logs everything that passes through the hardware keyboard port (0x60). It translates keycodes to ASCII with a keymap file.