Last October, NASA’s LCROSS mission slammed a spent rocket booster then the LCROSS spacecraft itself into the moon. No debris plume was seen from Earth, but observations from LCROSS of the booster hitting indicate the presence of water on the moon. How much water? Most news accounts don’t say, but the Science magazine article does.
100 kilograms of water was detected from an impact that created a crater estimated to be 20 m wide and 3 meters deep. So 100 kg water in about 500 m3 of regolith = 0.1 g/kg. (Googled a reference giving 2.3 to 2.6 g/cm3 as lunar regolith density).
The article gives a higher estimate for water, 0.1% to 10%, higher than my crude 0.01% estimate. Which is great–enough water to extract easily and live off. Best news for space exploration in thirty years!