Leaf is a (as I understand it) ShuttlePC system with an AMD Athlon 64 3200+ processor, 1GB DDR memory, USB / Firewire / GigE / other peripheral goodies, and a 160GB Maxtor HDD. It is very fast.
Access to Leaf is based on request; Matt Dillon is the man you need to speak to. It is required that you have been active on the DragonFly mailinglist or have contributed to the project to get an account.
There are many good books on programming in C. Some of the classics are mentioned here: