The Handshakes section of the website Ephesians5-11.org has information on Freemason secret signs, such as the Sign of an Entered Apprentice, Sign of a Fellow Craft and Sign of a Master Mason. The book, "A Ritual of Freemasonry," by Avery Allyn has illustrations of more secret signs.
Many Freemason secret signs are used to identify the user as a Freemason and as a symbolic gesture of a deeper truth or meaning. For example, to make the Sign of a Master Mason sign a person draws his thumb quickly across the waist to the right hip, then drops his hand to his side. This symbolizes the Master Mason's obligation to have his body cut in two and his bowels removed and burned to ashes as a penalty for betrayal.