These stocks are all down more than 30% this year.The S&P 500 (^GSPC 1.17%) is home to some of the best and most promising stocks you can own on the markets. When stocks in this broad index go on sale, it could be a prime time for investors to consider investing in them. Three S&P 500 stocks that have been crashing this year are attracting the notice of bargain hunters: Walgreens Boots Alliance (WBA -2.51%), Boeing (BA -2.09%), and Intel (INTC 0.71%). Let's take a look at why these three S&P 500 stocks are ...