Here is a list of some of the best websites out there that promote the game of cornhole. The ranking order is loose, but I'll give you some insight to why I like each site and what they have to offer.
1) CornholePlayers.net - This site seems to provide the most discussion about the game along with useful information for those who are new to the game. Building instructions, product reviews, tournament listings, and downloadable brackets are just a few of the resources offered by this site. The key attraction of CornholePlayers.net is the forum, in which newcomers can ask questions and search for answers about the game. I believe many search engine searches bring visitors to this forum for FAQs of the game.
2) AmericanCornhole.org - This website is the home of the governing body of the sport of cornhole. The ACO brings together the most competitive players across the country to compete against one another. The website offers a forum in which members discuss the future of the sport, tournaments, products, etc. It also provides the most complete set of rules on the web, a ranking system of the best players in the country, and an online store of the professional-grade products used in ACO competitve tournaments.
3) HoleMagazine.com - This site is the homepage of Hole Magazine, which is a newly published magazine to inform all about the growing sport of cornhole. The website features cornhole-related articles, news, blogs, and more. Visit this site to hear some interesting news going around in the cornhole world.
4) PlayCornhole.org - This is the American Cornhole Association's website. This site is also a good place to find information on how to play the game. The site offers its own set of rules, tournament postings, brackets, and other resources for visitors. Tournament postings are assorted by date, and cover a wide variety of locations in various states.
5) CornholeParty.com - I had to include another website that promotes the game through tournament postings. This site is great for finding upcoming tournaments in your state. The site also provides rules, board dimensions, and an online store to buy equipment.