OK, I turned on errors so I can see the problems. It's:

Fatal error: require_once() [function.require]: Failed opening required 'Zend/Service/Amazon/Query.php' (include_path='.:/usr/local/php5:~/ZendFramework-1.0.1/library/Zend') in /Users/dramsey/Sites/amazon-search.php on line 6

The thing is, Zend/Service/Amazon/Query.php does exist. Removing the initial "Zend/" from the require_once statement has no effect.

My include path looks correct as best I can tell, but obviously something's wrong.