flac2mp3 is a tool to convert potentially large sets of FLAC audio files into the MP3 audio format. It is implemented as a bash shell script, and should run on any Unix-like operating system.
You can get it at: bytemonkey.org
You'll have to install FLAC and LAME on your linux box, on debian/ubuntu this is easily done with
apt-get install lame flac
After you download flac2mp3 and untar it somewhere, run the script, feeding it with the source and destination directories:
/path/to/flac2mp3 /home/music/JimiHendrix_Experience/ /home/music/mp3/JimiHendrix_Experience/