I have a cheapo Bell Ukon helmet. I think it cost me about $40. I just bought a Bern G2 which is a multisport helmet with much better ventilation than the other skate/bike/ski type helmets. Additionally, the G2 has vents that can be opened and closed and has the option of being worn with a winter liner that has built in ear covers or a simple headband summer liner. I'm waiting for the summer liner to arrive since it's not quite cold enough here to be wearing it with the winter liner. I decided to give the skater/city bike type helmet a try because of the better lower head protection. Also, I'd been reading some articles about helmet design and crashworthiness and it seems as if the standard road bike type helmet has the potential of causing neck injuries in a crash due to the sort of "pointed" shape many of them have. Skate style helmets get higher marks in that regard because the more globular shape resists less when hitting objects in a crash scenario. Probably a minor thing, but something to consider nonetheless. I'll be interested to see how well the G2 breathes in really warm to hot weather. I see plenty of folks on my commute wearing skate style helmets in the heat of summer with far less ventilation than the G2. Somehow they manage it. They might be completely miserable, but I'm inclined to think that the G2 is probably a lot better in regards to ventilation. I'll find out soon enough.
http://bernunlimited.com/shop/bike/men/g2-w-visor.html