(The Settlers of Catan - One of the more popular board games amongst board game geeks.)
It's a gathering place with a great group of people who help each other out. It's a great place to find parts list, instructions, tips on where to find new or used games, plenty of community reviews to help you find the right game to fit your needs, direct access to many game designers and much more.
For example, I bought a brand new shrink wrapped copy of a board game called "Pirate King" that when I got it home and opened it up I found all the pieces were covered in mold. I had purchased the game at a shop several hundred miles from home while on vacation so I couldn't return it. It turns out the first edition of the game had some quality control problems (missing pieces, mold, etc.) and the entire stock had been scheduled to be destroyed. An unscrupulous person instead of destroying the games, sold them back into the supply chain. The game's author felt so bad that even though it wasn't his fault, he sent me a free second edition copy of the game at his own expense. He didn't have to do that, but he did and that's just one example of the great people you can connect with at http://www.boardgamegeek.com/
(Image borrowed from boardgamegeeks.com.)
If you decide to pick up a copy of Pirate King, go for the second edition (the one on the left). If you run across a copy of the one on the right (the first edition with a much larger box) DON"T BUY IT! Technically it's considered stolen property not to mention it's probably full of mold.