An interesting news release on the website of the Cassini Equinox Mission:
http://saturn.jpl.nasa.gov/news/cassinifea...feature20090904
I had noted that propane (C3H8) could also be present as a liquid on Titan. So, we have, at least, three potential candidates for pools of liquids on Titan: methane, ethane and propane.
If the data of wikipedia are correct, propane has a boiling point ( in normal, terrestrial conditons) of -42.09°C and a melting point of -187.6°C.
With environmental conditions similar to those in the landing site of the Huygens probe ( 1467hPA, -179°C), I suppose that propane can form liquid pools, as well.