No love for SQL Developer by Oracle?(Oops sorry didn't see it was mentioned earlier so I'll just second it.) We used to use TOAD exclusively but due to budgetary issues we reluctantly moved to SQL Developer. It was painful but after an adjustment period it is not bad. Does 95% of the functionality we used in TOAD. They do have a certified MacOS version :
http://www.oracle.com/technetwork/developer-tools/sql-developer/downloads/index.html
good luck!
P.S. it's free! it's not bad for a free product really...