Easiest way to install memcached on Mac OS X is using MacPorts (port) http://www.macports.org/
According to the MacPorts website…
The MacPorts Project is an open-source community initiative to design an easy-to-use system for compiling, installing, and upgrading either command-line, X11 or Aqua based open-source software on the Mac OS X operating system. To that end we provide the command-line driven MacPorts software package under a BSD License, and through it easy access to thousands of ports that greatly simplify the task of compiling and installing open-source software on your Mac.
The easiest way to install MacPorts on a Mac OS X system is by downloading the dmg for Lion, Snow Leopard or Leopard and running the system’s Installer by double-clicking on the pkg contained therein, following the on-screen instructions until completion. http://www.macports.org/install.php
Now, to install memcached, type the following command
sudo port install memcached
Memcached Server can be started by running the following command
memcached -vv
To run memcached as a daemon
memcached -d
These instructions have been tested on Mac OS X 10.6.8 (Snow Leopard)
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