CyanogenMod is an aftermarket firmware for some mobile phones based on the Android operating system.
CyanogenMod 7 is based on the Android 2.3.3 (Gingerbread) release, and currently supports 30 devices. It was designed to increase performance and reliability over stock Android-based ROMs, and also offers a variety of features and enhancements.
CyanogenMod 7 [article link]