I've been using the free Riva FLV converter, although I've tried many others too. One drawback of the PC based video converters is that they do not convert DVD video to flv. I always have to convert to an intermediate format first, like DivX. Another downside of Riva is, you can only do one video at a time. Riva actually uses a Winblows version of FFMPEG to do the conversion in the background.