One a more constructive note, the main one I find is:
http://www.nhoj.co.uk/icaldupedeleter/ But it doesn't seem to let you review what is getting deleted.
I just ran it myself & it cleaned up mine. I didn't have anything vital though, so you may want to back yours up before running just in case.
I now have one calendar in iCal called Work, that has my work events as well as (for some reason) phases of the moon. On iPhone, there are at two Work calendars, one with work events and moon phases, the other with just moon phases. HOW can i delete that second calendar?