Croctail lists the subsidiaries of a given company. For example, Coca Cola is listed as having dozens of subsidiaries.
Crocodyl is an interesting wiki for company profiles, although perhaps too basic for most competitive intelligence, particularly when Wikipedia itself does such a good job. For example, here is the profile for Abbott Laboratories:
CorpWatch's approach is that of a non-profit, so it is more interested in ethical abuses than competitive strategy, but the subsidiaries browser can be quite interesting.