HI,
I'm the guy that made the YouTube video Olly linked. I've created a notebook entry with some of the code: http://mbed.org/users/nandgate/notebook/websockets/
I did this as an experiment. The code isn't that stable, but it does demonstrate the capability. To make this "real" I would start with the LwIP stack and write the HTTP server from scratch (I had a hard time with the one provided).
Also, I will be giving a presentation on the late 2011 to early 2012, I can look into posting it to YouTube as well as I explain why this is important to embedded systems and how WebSockets work at the protocol level. If I do so it will be to the same YouTube channel as the demo video.
Ping me if you have questions.
Has anyone implemented websockets on mbed yet? Does anyone know where I can find any source which is easily portable? Any help would be greatly appreciated!