http://space.alglobus.net/ has some great resources that cover this area.  I hope he does not get upset but I'd like to rep[roduce a portion of his website here for all of you:

Space Settlement - Colonizing the Cosmos!

bring space to life and Life to space

"For me the single overarching goal of human space flight is the human settlement of the solar system, and eventually beyond. I can think of no lesser purpose sufficient to justify the difficulty of the enterprise, and no greater purpose is possible." Mike Griffin, current NASA Administrator, in 2004 testimony before Congress

Today space is mostly rock and radiation. We can change that. In the 1970's Princeton physicist Gerard O'Neill showed that we can build giant orbiting spaceships and live in them. These orbital space colonies could be wonderful places to live; about the size of a California beach town and endowed with weightless recreation, fantastic views, freedom, elbow-room in spades, and great wealth. In time, we may see hundreds of thousands of orbital space colonies in our solar system alone. Unlike earlier colonization events, no people need be oppressed and no ecosystems destroyed for the simple reason that there aren't any out there. If we do it, space colonization will be so important that only the origins of life itself is comparable. Even ocean-based Life's colonization of land half a billion years ago pales by comparison.

Space settlement provides an unparalleled opportunity for the United States. The U.S. is an expansionistic nation and there's a lot more opportunity to expand in space than on Earth. America has been expanding steadily from the day the first colony was established on the Eastern Seaboard. Today this expansion takes the form of a world wide military presence. This policy has some severe problems. Namely, some of the people in areas occupied by the U.S. military are well armed, royally pissed, and getting way too good at killing American soldiers. These sorts of problems are inherent in any expansion here on Earth. So, what if the U.S. spent it's money on space colonization rather than global military control?

• It's cheaper. The U.S. military budget is about $500 billion per year, far more than needed for space colonization.
• Fewer casualties. America has lost only 17 astronauts in 45 years of spaceflight, compared to over 2,000 American soldiers and a lot more Iraqis and Afghanis in the current wars alone.
• More real estate. The largest asteroid has materials sufficient for 1g living area equal to a couple hundred times the surface area of Earth (distributed into many colonies).
• More energy. The readily available, completely reliable solar energy in space is two and half billion times that available on Earth.
• More money to be made. One small Near-Earth Asteroid has about $20 trillion (yes, that's with a 'tr') worth of precious metals. Bottom line, there is a lot more wealth and power to be gained in space and you don't need to hurt anyone. Let's go!
• And perhaps most important, no one need be oppressed, no ecosystem need be destroyed, nothing is stolen, everything will be created from rock and radiation at no one else's expense.