Use Google Scholar to search for scholarly books and articles.
1) http://americanliterature.com/100-great-short-stories
2) http://www.englishlibrary.org/stories.html
3) http://www.classicshorts.com
4) http://americanliterature.com/twenty-great-american-short-stories
5) http://www.openculture.com/2013/10/read-14-short-stories-from-nobel-prize-winning-writer-alice-munro-free-online.html
The library has more than 500 databases where you can search for articles, images, audio files videos and more. The list of databases below is just a sampling of what's available. More library databases are available at http://ucmercedlibrary.info/doing-research/databases.