This plugin allows visual CC field editing.

A pop-up window with bunch of checkboxes is opened, user checks
boxes, email addresses are added and removed to CC field. There is
a list of pre-defined addresses in cc_selector.js (these addresses
will always be available). If you want to change this list you must
edit cc_selector.js manually.

Of course, you can always edit CC field without all this hassle -
all addresses you entered manually will be shown, too - and can be
removed with new, shiny checkboxes.

WWW: http://trac-hacks.org/wiki/CcSelectorPlugin