The T440p shows a thinkpad_acpi card and a snd_hda_intel card. To get audio working I had to disable the first by modifying /etc/modprobe.d/alsa.conf:
options snd_hda_intel enable=0,1
options snd slots=snd_hda_intel, thinkpad_acpi
options snd_hda_intel index=0
options thinkpad_acpi index=1
To get some more control over audio settings, install pavucontrol
To show live volume meter: pavumeter
Streaming to an Airport Extreme is easy, just run
sudo apt-get install pulseaudio-module-raop paprefs
and in PulseAudio Preferences tick the box Make discovarable Apple AirTunes sound devices available locally. After this you can select what audio output to use for each of your running audio programs in PulseAudio Volume Control. The only problem I'm still having is that the audio from some programs sounds choppy. VLC for instance wasn't working properly, but in my case rhythmbox works perfectly.
Other audio application suggestions found on this forum are totem, amarok, xine, mplayer, audacious, gmusicplayer and guayadeque.