1. A plaque: This plaque was attached to the lunar module's leg and read: "Here men from planet Earth first set foot upon the Moon, July 1969 A.D. We came in peace for all mankind."
2. A small, silicon disc containing messages from world leaders: This disc was about the size of a half dollar and contained messages from 73 world leaders, including messages in English, French, Russian, Spanish, Hebrew, Arabic, and Chinese.
So, while Armstrong didn't put anything on the moon in a way we might think of, he did leave behind a small but significant piece of human history.