I like my Bell Delirium:
http://www.performancebike.com/shop/....cfm?SKU=21137
In addition to fit, pay attention to how easy it is to adjust in the back. In colder weather, I may have alternating days where I do or don't wear a fleece skullcap under my helmet. I love how easy my Bell is to adjust tighter or looser depending on what's on my head each day.