Do you have a huge collection of LEGO sets at home that are no longer together and are just being used to booby trap rooms? I know as I walk through a room I have a chance of stepping on a LEGO and that really hurts. We have tubs and tubs of LEGOs that came from sets that have long since lost their instructions - or at least no one wants to build the sets anymore.

The website rebrickable you can:

Reuse your parts to build other Sets

Save money on buying LEGO by mixing up your current sets to build others. Rebrickable uses powerful algorithms to calculate what other sets/MOCs you can build from your existing sets and loose parts. If you don't have exactly the right ones, it will show close matches and can perform some fuzzy color matching logic.

In rebrickable you can create an account and enter all the LEGO sets you own... then get a list of creations you can build! So cool both for kids and adults.

Rebrickable will show you which LEGO sets you can build from the sets and parts you already own. You can choose from official LEGO sets or custom made MOCs (My Own Creations) by many different designers. All MOCs include building instructions, some of which are even better than the official LEGO ones!

I've always wondered if there is something that can be built with all the sets we have (and we have a LOT of sets).  The site does also let you look through possible creations.