The RouteBricks project seeks to enable networks that are easy to build, program and evolve. Networks have traditionally been built using special-purpose hardware and software which makes them difficult to extend, program or otherwise experiment with. Routebricks instead allows ordinary programmers to rapidly build and (re)program networks using the hardware and software platforms they are most familiar with that of the general-purpose PC. To achieve this, we are exploring a novel network architecture in which network packets are processed in software running on clusters of general-purpose PC hardware. This approach allows us to achieve high network processing speeds while offering significant advantages over specialized network equipment: lower costs due to large-volume manufacturing, a widespread supply/support chain, and, most importantly, programmability and extensibility.