I would add just for the the archive that the cmd line Pedro mentioned can be execute automatically by qjack after startup. see qjack options tab.
M
By the way... I just did the pulseaudio sink here on maverick, so I recalled this thread just to give the commands:
(from Ubuntu Studio, like previously said)
sudo apt-get install pulseaudio-module-jack
After jackd is started, launch in a terminal:
pacmd load-module module-jack-source channels=2; pacmd load-module module-jack-sink channels=2;
Easy as pie (not python). Now go to the ubuntu sound options, switch to pulseaudio on output (and in if you like) and enjoy. It is all routed back to jack by magical powers.