Great and easy Lego party ideas. Includes door sign printable and instructions on how to make a Lego head pinata out of an ice cream bucket! Also an easy way to make a Lego car track out of a folding table.
Build your own race car station -- this uses premade packs, but I'd think it might be more fun (and cheap) to fill at bucket with pieces at the store and let them be creative (Homemaking Fun: A Lego Themed Birthday Party)
57 LEGO Themed Birthday Party Ideas Perfect for Boys