The Analog to Digital Converter (ADC) on the BeagleBone is both a Touch Screen Controller (TSC) and a general purpose ADC. Depending on how many of the lines are reserved for the TSC (4, 5, or 8), the remaining lines can be used for reading analog values. One of the lines is connected to the power Management Integrated Circuit (PMIC, TPS65217) of the white Bone, in order to sense the power used by the board. This does not appear to be the case for the new BeagleBone Black.
If you liked the BeagleBone, you will love the next gen BeagleBone Black! With a blistering 1GHz processor, 512MB onboard DDR3 RAM, built in 2GB storage with pre-installed Linux operating system (no microSD card required!), and best of all, the addition of a MicroHDMI connector for audio/video output. This is a ultra-powered embedded computer that can fit in a mint tin.