Below is a chart showing the year to date performance of the Bloomberg IPO Index vs. the S&P 500. The Bloomberg IPO Index tracks is a basket of all stocks that have IPOd within the last year. As shown, the index is currently up 17.8% year to date versus the S&P 500's gain of 12.1%.
Below is a list of the top performing stocks (from their IPO price) in the Bloomberg IPO Index. As shown, InvenSense (INVN) is up the most with a gain of 145.6%, followed by Guidewire Software (GWRE), LinkedIn (LNKD), and Michael Kors (KORS). Other notable stocks on the list of IPO winners include GNC Holdings (GNC), Annie's (BNNY) -- which just IPOd this week, Yelp (YELP) and Zillow (Z).