|MadSci Network: Astronomy|
There appears to be two possible areas you are talking about---establishing a colony on Mars and the possibility of life on Mars.
Life on Mars has been raised as a possibility several times. Discoveries of subsurface water on the Mars and possible fossilized Martian microbes has raised the possibility of life existing on Mars in the past or even today. So far the evidence is being debated, and there is no conclusive answer. NASA is considering a mission to Mars that would bring back soil samples that could be analyzed for evidence of life. This would most likely be the closest to a definitive test to determine if there is life on Mars short of going to Mars with a manned mission.
Over the years, NASA and others have investigated the possibilities of sending ships to Mars to establish a colony. The journey is long (approximately 185 days), but within the scope of current technology. Once on the Martian surface, results from the Viking probes, Mars Pathfinder, Mars Global Surveyor, Mars Odyssey and other missions indicate we will have available considerable natural resources including water for drinking, oxygen and fuel. NASA and other nations are currently sending a series of probes to Mars over the next several years that will increase our knowledge of the planet and allow for a better, more likely to succeed mission at some future date.
Below are some examples of the various groups that are examining the colonization of Mars plus a couple of sites about Mars.
Try the links in the MadSci Library for more information on Astronomy.