With the release of Mac OS 10.8 (Mountain Lion), Apple changed how you gain access to make and gcc. In previous version of Mac OS you could install xcode and everything would work fine. In 10.8 the installation of the command line tools as a separate package is required. To make things more frustrating, while Xcode is available in the Mac App store, the command line tools are not. In order to get the command line tools, you must sign up for an Apple Developer account (a free account works).
Once you download and install the command line tools package you can download the MacPorts packages form their website at http://www.macports.org.
If you upgraded from Lion to Mountain Lion and had MacPorts installed prior to the upgrade, you will need to reinstall Xcode from the App store, then install the command line tools, then reinstall MacPorts. Then you will need to run port upgrade outdated to update your packages from the Darwin 11 version to Darwin 12. You may receive an error in reference to a library package. If that happens trying running port clean “packagename”.