Looking for a media player to playback your video converted to open WebM with Miro Video Converter, then grab Moovida media player. Open Source Moovida media player formerly known as Elisa is one of the first media players to boast support of the open source VP8 codec.
Moovida also supports wma, flac, flv, mpeg4, matroska(mkv), Theora and many more file formats. Its a free download for Windows and Linux. A Mac version will be out this summer. Ubuntu Linux users can install via the Software Center or using the terminal: sudo apt-get install moovida