Adafruit’s latest distro called Occidentalis is a custom build of Raspbian, a Linux distro optimized for better web browsing and general application performance on the Raspberry Pi. This software update adds sshd on startup, Bonjour networking, Wi-Fi adapter support, and other things to generally make the Raspberry Pi a better communicator with everything you’ve hooked it up to.
Although Adafruit calls it an educational Linux distro, Occidentalis was not designed for beginners. Instead, it was designed for hardware hackers, so you should know your way around Linux before you download it. Also note that this is big: You can download the four-gigabyte SD image of Occidentalis goodness straight from Adafruit’s site.