There are a lot of online resources out there for craft and home brewers alike. I figure that since this is a blog about craft beer business it would be appropriate to introduce the top 3 most valuable resources on the topic.
Craft Beer, www.craftbeer.com. This site helps you promote your events, collaborate with other brewers and breweries, they promote American Craft Beer Week, and in general support the industry. They have an active blog, facebook page, and you will find them on twitter @BeerWeek1. Go to http://www.craftbeer.com/news-and-events/american-craft-beer-week/resources for more on what they offer.
The Beeradvocate, http://beeradvocate.com/ is another great resource. Beeradvocate is also a monthly magazine publication. The website offers up to date information on beer and an ongoing blog about beer talk in general. They consolidate and promote beer events, offer multiple RSS forums of discussion, promote beers, and provide general information. You can also find them on twitter @BeerAdvocate and on google +
Brewers Association, http://www.brewersassociation.org/ promotes their platform as a passionate voice for the craft brew industry. They have a public web site but also a members only portal for specialized information. The Brewers Association is likely the most robust offering business tools in general from marketing to sell sheets to guidance on label approval and more. They have a government affairs section, a community section including a blog, promotion of beers and breweries, along with a history of the industry and of course event promotion. They can also be found on twitter @BrewersAssoc, and on Facebook. If you are in the business I have found Brewers Association to be a great resource.