The January 2010 Scientific American article "Looking for Life in the Multiverse" analyzes how much the laws of physics might differ while some form of life is still possible. It specifically shows that carbon-based life is still possible when the weak nuclear force is eliminated. The authors are less supportive of non-carbon-based life popular in science fiction, and still find support for the anthropic principle ("conditions that are observed in the universe must allow the observer to exist") in the precise value required for the cosmological constant.
Also, in an earlier post I claimed that all life on earth is dependent on the sun for energy. This is incorrect. The black smoker sea vents on the ocean floor support complete ecosystems including archaea, clams, and tubeworms. Here the energy comes from the interior of the earth instead of the sun.