Wikipedia
Thinstation
Thinstation is a free and open source Linux implementation of a thin client operating system. It only requires standard 32-bit x86 PC hardware and can boot directly from the network via PXE or Etherboot from a TFTP server, or from local devices such as Hard disks, CompactFlash drives, USB keyrings and CD/DVDs. The minimum requirement is an i686 class CPU and RAM dependent on the intended use, typically 64–256 MB.