Shovel up the Legos
From Kittenpie's wise family friend and mother of three:
When her daughters got to the age where they were playing with lots of small legos, a family friend of ours bought a large bin to store it all in and a kids plastic snow shovel. After spreading pieces all over the floor, she or her girls would simply take four or five passes over the carpet with the shovel to scoop and dump all those annoying little bits. Easy and fun, all in one.