Both Venus and Mars have good odds of having had liquid water oceans in the past. From what I understand, Venus would possibly be habitable today if it had a carbon cycle and planetary magnetic field to prevent the runaway greenhouse effect.
"Scientists once thought that no living thing could survive the harsh combination of toxic chemicals, high temperatures, high pressures, and total darkness at these vents. "
"Vent bacteria use hydrogen sulfide as their energy source instead of sunlight. "
http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/HTML/ps_vents.html