Can anyone tell me how to add to the classpath on OSX?
If you want to make a certain set of JAR files (or .class files) available to every Java application on the machine, then your best bet is to add those files to /Library/Java/Extensions
.
Or, if you want to do it for every Java application, but only when your Mac OS X account runs them, then use ~/Library/Java/Extensions
instead.
EDIT: If you want to do this only for a particular application, as Thorbjørn asked, then you will need to tell us more about how the application is packaged.