ExpertFlyer is well named - it is a site that caters to the frequent flyer. It is a service that you pay for - prices range from $4.99 a month for a basic plan to $9.99 a month or $99.99 for a year for premium services. ExpertFlyer aims to provide a "complete, concise and efficient way to access the ever changing details of worldwide air travel information." They do give you a chance to try before you buy with a 5 day free trial period.

The site has a wide range of features which I've looked at in Air Travel Tools, Tips and Resources - ExpertFlyer

Top Bank Air Miles Cards
Frequent Flyer 411 - A Guide to the Frequent Flyer Programs Around the World