To copy individual calendar items via e-mail just open the calendar item,
choose Actions | Forward (or Forward as iCal depending upon what app the
other person is using).
You could also export multiple calendar items (or your whole calendar
folder) to a PST file and e-mail that to them.
Finally there are some Internet Free/Busy options that might be a good
solution; depending upon your needs. Google for Internet Free/Busy if
you'd like more info on that.