Where do you think it likely that we'll find life, even the simplest forms of it, in our own solar system? Besides here on Earth, of course.
Mars looks less and less likely with each unmanned mission, and ever since Viking, tests have always proven inconclusive.
Arthur C. Clarke focused a lot on the Jupiter and its moons in his Odyssey series. A lot of attention went to quick-evolving life in the slushes of Europa, but I'm wondering if it isn't equally possible for something unique to thrive in the sulfurous lava lakes of Io -- if it can survive the violent tides of Jupiter's gravitational pull and its searing radiation.
Another exciting candidate is the Saturnian moon Titan, with a theorized soup of organic chemicals seething beneath the brown methane atmosphere.
What kind of shapes might these extraterrestrial lifeforms take? It's assumed that if there's anything, it won't more complex than simple microorganisms -- if even that. But even these would be an exciting find.