Contiki is an open source, low-power operating system for networked embedded systems. It includes the worlds smallest IPv6 stack and provides full IP networking in a few kilobytes of RAM, as well as low-power mechanism that makes a tiny radio-equipped microcontroller run for years on a pair of batteries. Version 2.4 has been released today.
As you would expect, this new release brings improvements (no way!), a number of bugfixes, and improved stability.
The low-power wireless MAC protocols have gotten an overhaul, improving power-efficiency and improved collision and interference handling. The COOJA/MSPsim simulation environment has received a significant speedup. Two new experimental platforms are included: the Crossbow MicaZ and the Sensinode CC2430/8051 platform. Many improvements and bugfixes has been made to the uIP code as well as the SICSlowpan implementaion of 6lowpan IPv6-over-802.15.4.
For more detailed information, you can peruse the changelog, and you can visit the download page to, well, download it.
This is just such a cool little OS, every release bring great features and fixes. really good stuff.
Near the bottom of the About Page are a list of additional contributors, mostly having to do with ports for different platforms. I copied the ones that had to do with platforms.
Groepaz. NES and PCEngine ports.
Ullrich von Bassewitz. Developer of the cc65 C compiler which is used for the 6502 ports of Contiki.
Lawrence Chitty. Sharp Wizard port.
Fabio Fumi. Casio PocketViewer port.
Matthias Domin. Atari Jaguar port.
Christian Groessler. Atari 8-bit port.
Anders Carlsson. VIC-20 port.
James Dessart. Tandy CoCo Color Computer port.
Chris Morse. Apple II port.
I know the emphasis now is for embedded controllers, but I still love the ports for older machines. I think the original example I saw was for the Commodore 64. There was a special network card someone made and you could use Contiki to sure the web! I think there was even a small webserver running on the Commodore 54 (IIRC).