Ffmpeg
The plugin is not available yet but here's how you can get it now:
- download VCD & MPEG Tools
- context click it and "Show Package Contents"
- go into "/Contents/Resources/"
- find the file "ffmpeg", see it?
- HOLDING THE OPTION KEY drag and drop that file into /Library/Application Support/kJams/
Now you're all set. Soon i'll just make an installer.