I ran into a string of errors while trying to run s3cmd with MacPorts python.

/opt/local/bin/s3cmd uses ParameterError before importing it. I moved the imports out of the try/except block to get this working:

if __name__ == '__main__':

    from S3 import PkgInfo
    from S3.S3 import *
    from S3.Config import Config
    from S3.S3Uri import *
    from S3 import Utils
    from S3.Exceptions import *
    from S3.Utils import unicodise
    from S3.Progress import Progress
    from S3.CloudFront import Cmd as CfCmd

    try:

        main()
        sys.exit(0)

    except ParameterError, e:
        error(u"Parameter problem: %s" % e)
        sys.exit(1)

Next, the command died while trying to import md5. The Python 2.5 port does not include hashlib, which defines md5. You can install it yourself like so:
sudo port install py25-hashlib

Lastly, while running s3cmd --configure and testing my connection with the HTTPS option, I got this warning:
WARNING: Retrying failed request: /?delimiter=/ ('module' object has no attribute 'ssl')

This feature depends on another port, which can be installed with:
sudo port install py25-socket-ssl