I just shot a bit of footage I wanted to upload to Facebook. According to this Facebook question, mpeg4 video is a good choice.

This command seems to do the trick to convert my rawdv footage to a Facebook friendly format:

cat foo.dv | ffmpeg -f dv -i pipe: -acodec libfaac -vcodec libx264 -s 640×360 -aspect 16:9 foo.mp4

Note that the names of the codecs in this command seem to vary according to your version of ffmpeg.  If this version doesn’t work, you might try faac and h264 instead of libfaac and libx264, respectively.