In the "not like us" camp is Michael Shermer, founder of the Skeptics Society:
Joining him is the History Channel, though I don't count them as a highly creditable source.
In the opposing camp of "possibly quite like us" is Simon Conway Morris, professor of paleobiology at Cambridge, who has been quoted by The Guardian as having said, "Extra-terrestrials … won't be splodges of glue … they could be disturbingly like us, and that might not be a good thing – we don't have a great record."
The article was about a two-day lecture series at the Royal Society, and goes on to state that
Conway Morris will argue that alien life is most likely to occur on a planet similar to our own, with organisms made from the same biochemicals. The process of evolution will even shape alien life in a similar way, he added.io9 has a post-conference article, and there are, of course, Youtube videos:
"My view is that Darwinian evolution is really quite predictable, and when you have a biosphere and evolution takes over, then common themes emerge and the same is true for intelligence.
"If you have a planet much smaller than ours, the gravity is so weak it loses its atmosphere. If the planet is much bigger, its gravity is so strong that everything crawls around on the ground, because you don't have to fall far to break everything. It's fantastically dull."
And finally, here's Michio Kaku on whether or not aliens are out there, and whether or not they want to contact us. Please ignore the weird kaleidoscope transitions.
* Just to make this absolutely clear, the people quoted below aren't the only people to hold their opinions. There are masses and masses of people that take either stance, and masses more who don't think there are aliens at all.