I think the inventory carried by retailers is more driven by marketing theme sets, but LEGO itself still carries generic building sets. (e.g. http://www.amazon.

I think the inventory carried by retailers is more driven by marketing theme sets, but LEGO itself still carries generic building sets. (e.g. http://www.amazon.com/LEGO-Ultimate-Building-Set-Pieces/dp/B000NO9GT4 http://www.amazon.com/LEGO-Ultimate-Building-Set-Pieces/dp/B...) You can even IIRC order specific parts in bulk directly from LEGO. But if you google, bulk lego, the most likely thing you'll come across lots of ways to pickup large amounts of used bricks from ebay or similar sources.