Tyler Nelson bought a box of 50 lego pieces and challenged himself to make 50 designs with it.
Here is his public Google+ page of photos of his fifty creations. Via Kottke.
Hmmm. The pieces look familiar to me. I gave my son a set with similar pieces. The three 'official' designs were for a fighter jet, a prop-driven plane like a WWII corsair or the like and...one other.
I played with lego from whatever age my parents first bought them into my teens and learned to make many different designs or items. Around 90% of my blocks were, well, blocky. They were square or rectangular and of uniform height. Oh, there were a few wedges, to make roofs properly.
Although I do like all the new parts and sets that are available, they feel very single-purpose. I still enjoy making the stuff with my son but it feels more like following a recipe than actual invention. A related question here is 'how much do I encourage my son to play with Legos?" I want him to have fun and play, not explicitly study and learn while using them. For this reason, I've been a little hands off. We make the origin designs together, then I leave them to him.
I've read that one serious blocker for creativity is too blank a page, too many options. Perhaps in my case the limits of square and rectangular blocks encouraged me to work around them and treasure the few pieces that were non-standard.