Encode something and both archive it in a WebM file and stream it as MPEG-TS over UDP:

ffmpeg -i ... -c:v libx264 -c:a mp2 -f tee -map 0:v -map 0:a
  "archive-20121107.mkv|[f=mpegts]udp://10.0.1.255:1234/"

As above, but continue streaming even if output to local file fails (for example local drive fills up):

ffmpeg -i ... -c:v libx264 -c:a mp2 -f tee -map 0:v -map 0:a
  "[onfail=ignore]archive-20121107.mkv|[f=mpegts]udp://10.0.1.255:1234/"

Use ffmpeg to encode the input, and send the output to three different destinations. The dump_extra bitstream filter is used to add extradata information to all the output video keyframes packets, as requested by the MPEG-TS format. The select option is applied to 'out.aac' in order to make it contain only audio packets.

ffmpeg -i ... -map 0 -flags +global_header -c:v libx264 -c:a aac
       -f tee "[bsfs/v=dump_extra=freq=keyframe]out.ts|[movflags=+faststart]out.mp4|[select=a]out.aac"

As above, but select only stream a:1 for the audio output. Note that a second level escaping must be performed, as ":" is a special character used to separate options.

ffmpeg -i ... -map 0 -flags +global_header -c:v libx264 -c:a aac
       -f tee "[bsfs/v=dump_extra=freq=keyframe]out.ts|[movflags=+faststart]out.mp4|[select=\'a:1\']out.aac"