Lunar Networks blog recently provided depth to the recent Journal Geophysical Research Letters research study led by Junichi Haruyama of the Japanese Space Agency JAXA and published in October 2009 from image and other data gathered by the moon-orbiting Japanese SELENE spacecraft. Linked is a radio show about lunar lava tubes.
Andrew Daga, a fellow grad of the University of North Dakota, recently proposed to The Planetary Sciences Division of NASA's Science Mission Directorate's Decadal Survey to study lunar lava tubes stating that "such a habitat would be completely protected from radiation, extreme temperature variations, and regolith dust. The implications for logistical and mission planners are that a substantially larger fraction of the landed mass can be dedicated to life support and science mission support. This could enable longer duration missions without risk of radiation overdosing, better reliability and a more diverse set of scientific technology, and a larger habitat area in which to work."