8 June 2015: GoogleCL is currently broken due to the OAuth1 turndown, and likely to remain so. Thanks for your support over the years, and apologies for the lack of prior notice.
summary Related Work
WARNING: Tips / links / claims found on this page haven't necessarily been tested by anyone affiliated with Google or the GoogleCL project. If you have a problem using one of these expansions, your best bet is to find and contact the original author.
GoogleCL on the Nokia 810 Internet Tablet
Android can run googlecl with a little work: http://publicint.blogspot.com/2010/06/build-talking-calendar-with-googlecl.html
This comment contains a bash completion script, and so does this github repo. To install one, copy it to /etc/bash_completion.d
Julien Danjou created a google-maps command for emacs
gcalcli is a neat python command line tool for using google calendar
A Google Groups management tool has been put together by Kurt (as descrbed in this post).