Free MP3 bitrate converter needed?

I'm writing a series of web tutorials for beginners. I wish to do one on converting the bit rate of MP3 files in particular and I want to direct my readers to the best free bit rate converter on the web. I'll base my tutorial on that converter, so it must be adware free and not shareware. (Yes, it can do other things.) I use C-Dex, but it's probably a bit complex for beginners. To save your time, please restrict your answer to the URL or the product's name. I'll downlaod and evaluate each program myself. I'll list all the sources you supply me in the tutorial but I'll only use one program as an example. Although my site is only a couple of days old and full of bugs, it's still worth a visit. The temporary address is a href="http://www.yacht-valhalla.com/answers" rel="nofollow"http://www.yacht-valhalla.com/answers/a Thanks for your help.