Ever since my son was 3 or 4 we have been diving him Lego sets. I've always been so impressed with how focused he gets when he gets a new set to build. I found this cool web site called Brickset that allows you to create a database of Lego sets you own. The personalized database gives you a lot of stats about the Legos you own. In some ways I really like this data that it gives me, must be the BIM manager in me, but when it tells me that from all the sets my family equals over 23k pieces I almost don't want to know the estimate value of those pieces.
Another thing that is nice is that from this website you can look up the Lego instruction manuals (or Maps as we call them). This is really good especially when the maps get misplaced, ripped, or just thrown away. But there is a functionality that allows you to look of maps of sets that you don't own and it tells you if you have the pieces to make the other set.
Earlier I was talking about how the database lets me see how many pieces my family has. You will notice that I didn't say how many pieces my son has. The reason for this is that we have gotten my daughter some sets, (which her brother puts together) but my Wife and In-Laws have gotten me some Architectural sets. With these Architectural sets I'm like Mr Business from the Lego movie and I don't let my kids play with them.
The other day I was looking at the Lego Architecture site to see what I new sets they have to add to my collection, and i saw a Lego set that really made me laugh. It wasn't a set of any particular building, but rather it was a set of a bunch of random sized blocks that were all white. They called this set the Architectural Studio. This set is a study model set. When I was in architectural school I never would have considered using Lego's to build a study model, but now I think it would be a cool idea. I almost want to get this set to create some physical study models of some of the projects I'm working on.