Is there any comprehensive source for landing fee information?
After working on the problem some more I have found there is not really any centralized source for landing fee information. Pretty much the only option is to call the FBO. However, you can get the FBO information from Flight Aware, assuming a US airport. For example, to get FBO information for Logan Airport in Boston, you would use the URL:

https://flightaware.com/resources/airport/KBOS

This tells you that the GA FBO for Logan is Signature and that their number is 617-561-2500. At that point you have to call them to find out more. For example, I did this and the answer was:

\$33 single engine piston landing fee
\$6 per hour parking
\$53.90 general landing fee
\$49.00 handling charge (waived if you buy at least 15 gallons of fuel) \$95 "security" charge
\$5 random bureaucracy charge