Today Mozilla Labs has released a new experimental add-on for Firefox, called Rainbow, which will enable video and audio recording in the browser.
The recorded media will be in an open-source format. Theora for video and Vorbis for audio in an Ogg contanier. The file can then be accessed in DOM using HTML5 File APIs and then be uploaded to a server.
This pre-alpha version of the add-on will work only with the Firefox nightly builds on Mac but support for Windows and Linux will be added soon. Mozilla also wants to enable live streaming of video feeds.
Download: Rainbow | Firefox Nightly build | Source code