Independent test site dedicated to motorcycle helmets. Price has little to do with performance which is good news, and tons of useful information about helmets in general.
It's a British site so some of the helmet names are different but you should be able to find the major manufacturer's products.
Interestingly there are NO current Arai helmets with a 5 star rating.
Also interestingly, every single Bell helmet regardless of price is 5 stars.
As I heard recently, "You can buy the best helmet out there, but it's what you put inside it that's most likely to save your life".