What are the best ways of gathering information on events (any type) from the internet ?

Keeping in mind that different websites will present information in different ways.

I was thinking 'smart' web crawlers, but that can turn out to be extremely challenging, simply because of the hugely varied ways that different sites present their information.

Then I was thinking of sifting through the official twitter feeds of organisations, people with knowledge of events .. etc and look for the event hash tag, grab the tweet and dissect it to grab the relevant information about the event.

Information I am interested in gathering is: Date and Time of Event, Address where Event is being held, and any Celebrities (or any famous people) attending the event (if any).

The reason to ask here is my hope that experienced folk will open my eyes to things I've missed, which I am sure I have.