I was getting tired of converting each individual flash video to mpg by hand, so I wrote a script to convert every .flv file in a directory.
for f in *.flv ;
ffmpeg -i "$FILE.flv" -target ntsc-dvd -s 320×240 "$FILE.mpg"
My biggest problem was to get ffmpeg to recognize filenames with spaces. ffmpeg, for that matter most command line applications, see spaces as file separators. After trying many things I found using double quotes did the trick.