OS X essentiality MacPorts has a convenient command line user interface for querying and browsing available software packages. For instance a simple "ports info pine” will net:

pine @4.64 (mail)
Variants:             darwin_9, ssl_plain
Description:          Pine is a tool for reading, sending, and managing
                      electronic messages that was designed with novice
                      users inmind.
Homepage:             http://www.washington.edu/pine/

Platforms:            darwin
License:              unknown
Maintainers:          sean@fuzzymagic.com

A more graphical option for the occasional port lookup is to use OS X built-in file indexing system Spotlight that happily provides as-you-type matching of available ports in the local ports tree.

The corresponding port file directory will typically be the top match when searching for well-known unix software.