In case you wish to know about the popular categories and search keywords that show Adsense ads of maximum CPC, here’s a list arranged in categories.
e-Commerce: VoIP, Broadband, Domain Names, Web Hosting, Web Design
Lifestyle: Fitness, Dating, Singles, Education, Degrees
Travel: Airline, Car Rental, Hotels, Cruises, Vacations
Real Estate: Mortgages, Refinancing, Home Equity Loans, For Sale by Owner. Credit Score
Financial Planning: Loans, Credit Cards, Debt Consolidation, Stocks, Payday Loans
You can see the latest image and text ads in Google inventory for the above keywords using the Adsense Sandbox.
What’s missing from the above list of top paying keywords are the health care and legal help categories that are known to pay in excess of $20 per click - they include search terms like mesothelioma, asbestos, accident lawyers, attorney, etc which fetch the highest Adsense CPC rate but only for real sites.
Related: Google Adsense Arbitrage