Systems Research Group, Networks and Operating Systems  
   University of Cambridge, Computer Lab. Many interesting network OS oriented projects, including Nemesis OS.
   http://www.cl.cam.ac.uk/Research/SRG/netos/

Network Research Group  
   University of California, Irvine.
   http://bolero.ics.uci.edu/

x-kernel  
   Object-based framework to implement network protocols; defines an interface that protocols use to invoke operations on one another (i.e., to send messages to and receive messages from adjacent protocols) and a collection of libraries to manipulate message
   http://www.cs.arizona.edu/xkernel/

KA9Q NOS TCP/IP Package  
   Second known implementation of Internet protocol (IP) for low-end computers; can at once be network client, server, IP packet router; support multiple client and server sessions. Description, downloads, zip format. Original author.
   http://www.ka9q.net/code/ka9qnos/