MARCH 1 SAN FRANCISCO6th annual Celebrity Crab CrackingPlayers for the San Francisco 49ers show they have finesse as well as muscle when they team with Bay Area chefs to provide a crab-cracking how-to demonstration. After the demo, the players, the 49ers' Gold Rush cheerleaders and local VIPs compete in a timed crab-cracking-and-cleaning contest. Visitors can sample Dungeness crab and follow it with sips from the Wine & Beer Garden. Cost: Free admission; tickets for tastings of food, beer and wine are $5 each or six for $25. Where: Union Square, 301 Post St. Info: (415) 781-7880, www.unionsquaresf.net.