Coalition for Space Exploration
Here is a link to the Coalition for Space Exploration, a Space Advocacy blog with a journalistic bent... 
Secure World Foundation
The Secure World Foundation looks at promoting peaceful uses of space for all humanity. 
Mars Underground - Lava-tubes
In 2009, the Geologic Society of America held their annual conference in Portland, Oregon. As part of that event, Dr. Penny Boston and I hosted a field trips to the "Cave Flow" on the South slope of Mt. St. Helens. This site offers a great primer of the lava-tube concept.