Official DiabloMiner.app
It's hosted at github.

Downloads are here.

It's open source, so you can check the code to see how safe it is.

There's an old but still active thread on the bitcointalk forums.

It looks like the program is java code and so doesn't need compiling for OSX, and also that there's a script DiabloMiner-OSX.sh that runs it on OSX.