CNBC announced today registration is now open for the second "CNBC.com Million Dollar Portfolio Challenge." Contestants compete for a grand prize of $500,000 and various other cash payouts and weekly prizes ranging from Super Bowl tickets to a trip to Turks and Caicos.

Trading begins on May 12 on CNBC.com and lasts for 10 weeks. Contestants receives $900,000 CNBC Bucks to trade stocks with and $100,000 CNBC Bucks to trade currencies. Last year's winner, Mary Sue Williams, an Ohio waitress, had never previously bought a stock in her life.

The contest doesn't just benefit viewers — last year's contest nearly tripled CNBC.com's site traffic.