If you're anything like the average LEGO collector, you've probably picked up a number of sets over the years, built the awesome looking things on the boxes, maybe kept them on display somewhere for a little while until you ran out of shelf space, and then relegated all the blocks to some giant communal LEGO box somewhere. In the end, you wind up with a massive box of LEGOs and the instructions to build things that would only require a tenth of them, things you've already seen to boot. Well, no more.
Rebrickable aims to help you use your entire LEGO collection to help you build sets that you never bought, but have the blocks for. All you have to do is enter the serial number of the sets you have, whether you want colors to match exactly, close, or not at all, and Brickables will tell you what awesome sets your sets can become when their powers combine. The best part is that the database includes both official LEGO sets and some custom ones that are way cooler than the multicolored monstrosities you free-styled as a kid. If you wanted to pull out your LEGOs again, but don't necessarily feel like recreating Hogwarts or whatever the kids are into these days, Rebrickable is the way to go.