I'm not an IA person at all, but one of the challenges I occassionally revisit is what would I do with something like the National Weather Service [weather.gov] site?
There's a huge amount of information spread over different agencies, domains, subdomains, etc., each of interest to different constituencies.
How would you even begin to get a handle on something like this? Define your users? Define your content? Or treat it like spaghetti, throw it on the wall and see what sticks?