"Enthusiasts without capacity are the really dangerous people." —Lichtenberg, Aphorismen
My work around here varies from day to day. I participate in page expansion and cleanup, editing, adding new entries, and adding pronunciations. I periodically add quotations from books that have entered public domain, which often results in new entries, new senses, and definition cleanup.
Perhaps the biggest effort I made was contributing towards Latin and Galician. I used to be heavily involved in coordinating the Word of the Day selections, but have since turned that over into other capable hands.