The MacTeX Working Group from the Tex User Group (TUG) constructed an install package which installs everything needed to run TeX on Mac OS X in one step. This package is free, and uses Apple's standard installer; installation takes four to eight minutes and is automatic. The package installs TeX Live, the complete reference edition of TeX produced in cooperation by TeX User Groups across the world. It also installs several front-ends for TeX including TeXShop (a perennial favorite), so it is not necessary to find an editor separately. Everything is completely configured and ready to use once the installer finishes its job.
The package is called MacTeX and is available at the MacTeX web page: http://www.tug.org/mactex.
Happy TeXing.