Today, St. Patrick’s Day 2010, millions of people will don green and celebrate the Irish with parades, good cheer, and perhaps a pint of beer. But pinning a shamrock to your lapel in 2010 may require a heaping helping of the luck of the Irish.

Find out why shamrocks are in short supply, what St. Patrick really did, and more in our no-blarney roundup of St. Patrick’s Day facts.