I've been using OSX as my main desktop OS for about a year now, and it's unbelievable how many simple customizations require third party products. To make it worse, a lot of them cost money.

Coming from Debian and Fluxbox I'm used to almost any possible configuration or customization being possible via /etc, the files in ~/.fluxbox/, or utilities installed using synaptic.

Here are some little known Mac utilities I like:

* MutableCode's Breakaway let's you configure separate audio volumes (including silence) for with and without headphones.

* Stereopsis' Flux adjusts your display's color temperature to match the type of lighting in your room (e.g. daylight, halogen, fluorescent) to avoid the blindly blue glare in a dark room.