I find myself wanting to link to further information about a game or expansion fairly often. When describing something, it's nice to provide a link so the reader can find out more. But there are frequently several good choices of what to link to, and I'm not sure which to pick.
BoardGameGeek has a ton of information, including categorization of games, recommended numbers of players based on user votes, a description, reviews, discussion, file uploads for player aids and rule translations, and so on. On the other hand, the page is extremely busy, it can be hard to navigate, and you sometimes have to click through quite a lot to find all of the information it has to offer.
For many games, Wikipedia has a good article on the game. On Wikipedia, you have a much cleaner interface, and see pretty much all of the relevant information on one page. It doesn't have as much information on precisely categorizing games, reviews, ratings, or the like, but for the information it does provide, it can be easier to navigate. It also sometimes provides historical background or other information that BoardGameGeek does not or may be hard to find on BGG.
Then there's the official site for the game itself. These vary in quality; some of them just provide very basic information in the form of a blurb and a box cover. Some of them provide a good deal of information, like rules, strategy guides, errata, payer aids, and the like. They are generally promotional in nature, so you get to see how the company is trying to sell their game rather than what other people think about the game.
Another option is to link to Amazon or another online store. This allows anyone interested in the game to buy it right away, and will generally have some description and review information, but may not be appropriate for everyone on the site as other online stores might be more appropriate depending on their country.
When you're reading about a game in an answer, which of these sites do you prefer to get a link to? Is there a good rule of thumb about which link or links I should provide?