Install R on Mac OSX

Preamble
How to install R onto a Mac. It's very easy.

The R site is here: http://www.r-project.org/

The Mac OS FAQ can be found here: http://cran.r-project.org/bin/macosx/RMacOSX-FAQ.html
The FAQ answers questions such as, What machines does R for Max OS X run on?, How to build from source code?
There is also a section on the R.app - that is the GUI application for the Mac.

What releases of  OS X
R will run on Mac OS X version 10.2 (Jaguar) or higher.
The GUI application for the Mac requires Mac OS X 10.3 or higher (Panther).

Download and Install
To download R for the mac goto a mirror. The list is on the CRAN page.
Visit the R site is here: http://www.r-project.org/

When you have found a suitable mirror site, download the pkg file.

Run the pkg: and get to this screen and follow the installation through.

Run the R app as normal to start the application.

Job done
That's it. A 32-bit and 64-bit version will be installed.
Getting started
R can be used a simple calculator, for example:
> 2+3
> log(10)
> 3^3
> (2*3)+6
>sqrt(81)

The cheat sheet can be found here. It's useful in getting started.

R used as a simple calculator