Contiki

[Fact 1]: The name Contiki comes from Thor Heyerdahl's famous Kon-Tiki raft.Despite providing multitasking and a built-in TCP/IP stack, Contiki only needs a few kilobytes of code and a few hundred bytes of RAM.

[Fact 2]: S a small, open source, highly portable, multitasking computer operating system developed for use on a number of memory-constrained networked systems ranging from 8-bit computers to embedded systems on microcontrollers, including sensor network motes.

[Fact 3]: A full system, complete with a graphical user interface, needs about 30 kilobytes of RAM.The basic pre-emptive multithreading

Protothreads

TCP/IP networking, including IPv6

Windowing system and GUI

Networked remote display using Virtual Network Computing

A web browser (claimed to be the world's smallest)

Personal web server

Simple telnet client

Screensaver

Contiki main website

C64WEB.COM A web site run from a unmodified 1982 Built Commodore 64

inofficial Website for historic ports of the 1.x version

The news about IPv6 stack

Minimal Contiki OS for LPC2103 .