Open your heart, open your mind!

two steps, messy but effective

first you need software:

ffmpeg Terminal: sudo apt-get install ffmpeg
winff from http://www.biggmatt.com/winff - (OR - http://www.winff.org )
Mobile media converter from http://www.miksoft.net/mobileMediaConverter.htm

(format table FOR MOBILE MEDIA CONVERTER:
from amr to mp3
from mp3, wav, wma to amr
from wmv, mpeg to 3gp
from 3gp to mpeg)

flv to 3gp

Use winff to convert the flv video into wmv format then use mobile media converter to convert the wmv file into a 3gp file
NOTE: i believe the latest version of mobile media converter now handles flv files

3gp to flv

use mobile media converter to convert the 3gp to video for computer (only outputs as mpeg) then use winff to convert the mpeg into flv or other desired format

source: http://ubuntuforums.org/showthread.php?t=481595

Added: 14.12.2009. - Yet another good converter 4 linux with GUI interface - tabencode - http://devel.zs4.org/tabencode_linux.html

You can also listen free music on T@b radio - http://www.thugsatbay.com/tab/files/tabradio.m3u

And a REAL MEDIA CONVERTER 4 linux - http://syntux.net/blog/2008/06/02/simple-real-media-converter/