Even if you don't believe all the hype about HTML5, sooner or later, you'll need to start encoding some video to WebM format. Maybe for internal experimentation, maybe for a pay-per-view or subscription project (where H.264 may incur royalties), or maybe because you've decided to jump into HTML5 video with both feet. Basically, Miro Video Converter is free, very easy to use, and adequate for getting a quick free look at WebM. But it's not useful for serious encoding because there are zero encoding parameters -- you just input the file, choose a preset, and start encoding. Firefogg is another frequently mentioned free WebM encoding cool that does more than Miro, but it still falls into the technology demonstration category, again, due to the lack of control over output parameters. Telestream Episode has an exceptionally simple WebM encoding interface that produced very good quality files, but it had some interactivity playback issues in Google Chrome that were concerning.