Format Factory It's 100% free, just make sure you uncheck the Ask.com toolbar option when you install it. Also, it defaults to automatically check for updates. I always turn that stuff off so things aren't poking at my bandwidth in the background.
It's lightning fast. I convert FLV's to MP3 all the time with it. I don't know what codec it uses for MP3's but they sound great. It also converts video from cell phones to any format, MPG, WMV, etc.
Hard to believe it's free ... it's the best converter I've ever used.