Viral Spy is a 100% free desktop application that will crawl your competitors website checking each page to see how many Facebook shares, Google Plus Tweets and LinkedIn shares it has. It it can extract a date from the page it will even calculate the share velocity for you so you can tell which pages were shared the fastest.
Simply enter your competitors website and click start, its that simple. All links are extracted as the crawl goes along so you don't have to do anything.
If you want your content to go viral then you need to know what people want to share in your niche, a great way to do that is to simply look at what your competitors website visitors are sharing on social media.