If you don't need more than 6 at one time you could consider a chip like the 74HC4051 analog multiplexer. It would allow you to connect up to 8 analog sources to a single analog input of the arduino.
A copy of the datasheet for the chip is available at Intelligent Power and Sensing Technologies | onsemi
Since I don't believe the AVR can sample multiple analog channels simultaneously this chip just adds a bit of overhead and could give you up to 48 (6 arduino * 8 ch/74HC4051) analog channels on a single arduino!