Peeron

(Guest written by Daniel)

Peeron is a database listing the parts of each and every LEGO set known to man. Founded by Dan and Jennifer Boger in 1998, Peeron lets you dig through that giant box of loose LEGO pieces in the attic and find only the parts you need to build that favorite pirate ship of yours. And if you don't have the instructions either, Peeron also supplies scans of the instructions for sets at least three years old. The inventory also works by part: you can see which sets have which parts in which colors--good if you're building something and you need something exact.

If you're a LEGO nut, it's fun to aimlessly browse through and see all of the technical names given to the pieces. When I was a kid, Brick 1 x 1 was known as a "onesie", but now I'm sure there are plenty of adults that call it by its number, 3005. Here's one of my favorite sets--I told my grandfather that I wanted it for Christmas real bad, and, well, like any good spoiled child, I got what I wanted for Christmas.

Kids aside, AFOLs (Adult Fans of LEGO) actually form a pretty strong part of the LEGO-buying crowd, and they meet where else but the interwebs. They are the ones who maintain Peeron and add new inventories, as well as pay those enormous eBay prices. If you've got a large enough collection, it's worth it to add a Peeron account and add all of the sets you own to your own set database, effectively telling you every piece that is in your collection. So, I have 618 1 x 4 Bricks, and 209 of them in black. Peeron will even use your inventory to attempt to build sets you don't own, telling which parts you have, which you don't, and which are in the wrong color. Pretty useful, if you're a crazy person.

(From Daniel Spaniel)