I have a problem getting PyDev on eclipse to recognize already installed modules. Here is my detailed approach. The machine is a Mac (Snow Leopard).
In terminal the
You can simply add the module to the pydev path. Go to project properties (from the context menu) -> PyDev -> PYTHONPATH -> External Libraries. Depending on whether the module is in a source folder or a zip/egg file, select either Add source folder or Add zip/jar/egg. Navigate to the site-packages directory and point to the relevant file or folder (mine is: /usr/local/lib/pythonx.x/site-packages)