I was looking for out-of-the-ordinary helmets a while back. There are a bunch of cool motorcycle helmets available ("cool" being relative here), but they don't necessarily meet the motorcycle helmet standards. In other words, legally, they're hats.

Unfortunately, the only bike helmets I saw that weren't the same-ol-same-ol were the skateboaring/bmx helmets, when tend to not be ventilated as well.