iodine is a implementation of a DNS tunnel written in C by Erik Ekman and Bjorn Andersson. It needs the TUN/TAP device in Linux. According to the website iodine is faster than other DNS tunnels (about 1MBit/s) and provides more security through password authentication. It allows 16 users on the server at the same time.
The most recent version is 0.6.0-rc1 from February 2010.