The Apollo missions provided a dramatic inventory of lunar surface samples. For safety reasons, however, astronauts were limited to the near side, equatorial region of the Moon, so they sampled a relatively small area. All of the sample sites outline only 4 to 5 % of the lunar surface. Thus, there is much more exploration to be done.
After Apollo, it was realized that impact events on the lunar surface eject material into space that falls to Earth as meteorites. Dozens of lunar meteorites have now been found. These are essentially free planetary samples, because nature has delivered them to Earth, without the cost of a spacecraft mission.
These are invaluable samples, because they represent a much broader region of the lunar surface. Indeed, they are launched from all areas of the Moon, including the far side of the Moon, which lies hidden from our view. Although we can use chemical fingerprints to identify the approximate source region of the meteorites, we are unable, unfortunately, to precisely locate their launch sites. For that reason, the samples are without geologic context and some scientifically useful information is missing. Nonetheless, these samples have proved to be a spectacular asset to our studies of the origin and evolution of the Moon.
Two good summaries of lunar meteorites have been assembled. The first is by Professor Randy Korotev at Washington University (in St. Louis). For interested readers, we direct you to his lunar meteorite website. The other good summary is The Lunar Meteorite Compendium that was compiled by Dr. Kevin Righter at NASA’s Johnson Space Center. Many of the lunar meteorites described at these two web sites were recovered by the Antarctic Search for Meteorite (ANSMET) program , which is jointly operated by the National Science Foundation and NASA. Additional details about the processing and curation of the meteorites is available from the Antarctic Meteorite Curation Office at NASA’s Johnson Space Center.