The sub-command `reclaim` is quite useful for freeing up disk space.
`reclaim` is a useful command that is missing from the list of completions in the plugin.

The description is for the `reclaim` sub-command is:
"port reclaim will find files that can be removed to reclaim disk space by uninstalling inactive ports on your system as well as unnecessary unrequested ports, and removing unneeded or unused installation files. The user is then provided interactive options for files to remove. No files are removed initially, until the user selects them from the provided list."

For all the details use this command on a system with Macports installed:

`port help reclaim`