I can't seem to find the my.cnf or other config file for the MySQL that comes with MAMP. Does it not include one?
The MySQL server of MAMP (not PRO) will be started without any my.cnf file. But you can create your own my.cnf file.
You do not have to put a complete configuration in the my.cnf file. You can just add parts of a configuration ... for example:
[mysqld] max_allowed_packet = 64M