Board Game Geek is a website, database, and forum covering "not only board games but also dice games, card games, tile-laying games, and games of dexterity." It's a remarkable achievement - impressively thorough and detailed. Each game lists facts about the game - how many players, average playing time, age range, game designer and other credits, alternate versions and expansion options - along with community input including ratings, comments, and player reviews, both written and video. There are extensive photo galleries, which are wonderful ways to get a sense of each game.
I first came across Board Game Geek when I was looking for information about the Masterpiece game I had as a kid. The edition I had included postcard-size images from the Art Institute of Chicago, a museum I visited pretty regularly as a kid growing up in the Chicago suburbs. Playing the game gave me a surprising familiarity with the paintings, which I remembered years later in all kinds of different contexts.
I loved it so much that one of my few eBay purchases was a copy of the game, just so I could get my hands on that collection of postcards.
The entries at Board Game Geek classify each game in a variety of categories - things that I, as a very minimal gamer, know nothing about but find fascinating: game mechanics (things like dice rolling, grid movement, constrained bidding, and stacking and balancing), game themes or topics or families (ancient Babylon/Corinth/Egypt/Pompeii; animals: foxes, horses, goats, mice, octopuses; cities: Bremen, Cairo, Caracas, Liverpool, Lviv, Nagano; decades: the 1920's, 1950's, 1980's), and categories (Farming, Bluffing, Territory Building, Transportation).
One of my favorite features is the information on Language Dependence, which tells you how language-dependent components (aside from the rules) are for those who do not speak the game's published language. (For example, Masterpiece has "Some necessary text - easily memorized or small crib sheet," while Lost Cities has "No necessary in-game text" and Blue Moon has "Extensive use of text - massive conversion needed to be playable.")
It's an absolutely gobsmacking amount of information, and it certainly seems like the kind of thing that wouldn't be possible without the volunteer work of a generous and enthusiastic community.
I recently rediscovered Board Game Geek thanks to an appreciation of game designer Reiner Knizia at MetaFilter.
I am not the target audience for Board Game Geek (I really enjoy board games, I just rarely get to play them), but I am beyond delighted that it exists, and that I can go poke around and explore the world of thoughtfully designed, cunningly crafted games any time I like.