I setup PyDev with this path for the python interpreter /System/Library/Frameworks/Python.framework/Versions/2.5/Python since the one under /usr/bin were alias and Eclipse won\'
I know this is a ancient post... but, in case of some newbee like me to get the better answer.
I just using "Eclipse Marketplace" from the "Help" menu and search for keyword "python" or "PyDev" to get PyDev, and get it successfully installed.
AND, you should add PyDev to the top-right dock.
For the instance, my eclipse on my laptop's OSX is (Version: Indigo Service Release 2 Build id: 20120216-1857).
Have fun, folks! :)