A few years ago I ordered my Monarch tagging kit from Monarch Watch. It's helpful to track the Monarchs migration to Mexico or anywhere they are captured. Being they are threatened every bit of info counts. They even let you know if your monarch was found, and the location!
You can order your tagging kit and data sheet from their website, as well as milkweed (host plant) and Monarch way stations which provide safe habitat for wild monarchs to breed and feed.
I think as many who can participate should every bit of help counts! http://www.monarchwatch.org