When using Cordova CLI, you shouldn't install plugins using plugman. Cordova CLI does use plugman under the covers, but what you want to use is cordova plugins add http://...
or cordova plugins add /path/to/plugin.xml
.
You didn't specify which version of Cordova you are using, but here's some examples of adding plugins that are core functionality: http://cordova.apache.org/docs/en/3.0.0/guide_cli_index.md.html#The%20Command-line%20Interface