That Firefox thing doesn't work in FF3, though.
For converters, try
FFMPEG: it's so awesome that it can only be contained in a command-line utility and
might be illegal in the USA

It's a good converter of anything to anything. ASF, AVI (yay copyright Microsoft), BFI, IFF, RL2, FLV (yay copyright Adobe), Matroska, Maxis XA, MSN Webcam stream, MPEG, TXD, OMA and WMV (more copyright Microsoft) and a lot more.