I see someone else already mentioned the official MySQL Browser. Be forewarned, however, it is more than a little buggy for OS X. Not all features have been implemented yet either.
Another tool I believe worth mentioning is Aqua Data Studio. It is free (non-commercial), built in Java (but thankfully not too noticable) and allows multiple connections from MySQL and PostgreSQl to Oracle and MS SQL. I am a DBA by trade and this tool has replaced nearly all others I've used for maintaining and working with my various disparate databases day to day.
Oh, and MAMP? I've never liked the acronym and I suspect many others do not as well. I've always prefered XAMP. (Yes I know someone released an installation package called XAMP, but the acronym existed before that)