Enter the Box4Blox ($40 including shipping). The sorting and storage unit comes with four different trays, each outfitted with a series of descending grids. Simply pour a pile of LEGO pieces through the top and watch as the bricks filter their way through the system. When the sorting is through, four boxes of blocks, bricks, and pieces will be separated by size and ready for play.
As a mom, I love the inspiration that a set of LEGOs gives my tots. But as a neatnik who tries to keep an organized home, I can't stand having to sort through large tubs just to find the one lil piece we need to complete our latest creation. We've tried using different colored tubs and bins for various sized bricks, but within days, they are all mixed together and we are right back where we started.