stream with ffmpeg, pulseaudio.

default.pa

# To record both mic and other audio input sources we need to add a named output sink. See:
# http://www.linuxquestions.org/questions/linux-software-2/alsa-and-pulseaudio-recording-multiple-input-devices-877614/
# http://www.youtube.com/watch?v=oJADNOY615Y&feature=player_embedded
# Add this to your /etc/pulse/default.pa file

load-module module-null-sink sink_name=stream
load-module module-loopback latency_msec=5 sink=stream
load-module module-loopback latency_msec=5 sink=stream

stream.sh

#!/bin/bash

STREAM_KEY="<justin.tv stream key>"
INRES="hd1080" 
OUTRES="hd720"
FPS="24" 
QUAL="fast"  

ffmpeg -f x11grab -s "$INRES" -r "$FPS" -i :0.0+1680,0 \
    -f alsa -i pulse -ac 2 -vcodec libx264 -preset "$QUAL" -s "$OUTRES" \
    -acodec libmp3lame -ar 44100 -ab 128k -threads 0  \
    -f flv "rtmp://live.justin.tv/app/$STREAM_KEY flashver=FMLE/3.0\20(compatible;\20FMSc/1.0)"