I found this command that successfully strips the audio into a wav file:
ffmpeg -i Blessed_Be_Your_Name.flv -vn -acodec pcm_s16le \ -ar 44100 -ac 2 Blessed_Be_Your_Name.wav
Here is the same command that includes the video that will play in Window’s Media Player:
ffmpeg -i Blessed_Be_Your_Name.flv -vcodec msmpeg4v2
-acodec pcm_s16le \
-ar 44100 -ac 2 Blessed_Be_Your_Name.avi
I was able to use this command to convert an flv file from a downloaded Google Tech talk to an mp4 file that I could play with mplayer in Linux:
ffmpeg -i Using_bluemail_to_renew_the_design_and_study_of_enterprise_email.flv \ -vcodec xvid -acodec pcm_s16le -ar 44100 -ac 2 \ Using_bluemail_to_renew_the_design_and_study_of_enterprise_email.mp4