ITA is only the absolute best resource for finding fare information. To quote their website, ITA Software's QPX system is the world's leading airfare pricing and shopping system. It's the engine behind Expedia, though much more full-featured - the only thing you can't do is actually book the fares... Go to http://matrix.itasoftware.com/, pick your flights and select "show booking details". It'll show you the base fare, taxes, and fees. You need to create an account, but it's not a big deal.