I found this post from Jeff Jarvis of BuzzMachine Two kinds of content (scroll to the bottom):

Looked at that way, there are two kinds of content in the world: reference (fed by wiki so it can be updated) and feed (rss, fed by blog software).

The former is lasting but needs to be updated; the latter — news, conversation — is timely and flows.

Quite right. I’ve been trying to explain this as time focussed content (better for blogs) and subject focussed content (better for a wiki if the content is evolving, or just PDFs for snapshots in time). I think “reference” and “conversation” are a good ways of describing the distinction as well. Feed, however, doesn’t quite get at it because if you’re interested in the subject you’re going to subscribe to the feed of the wiki page because it’s evolving.

I’m sure people can come up with many more kinds of content on the web, metadata is one, but these two seem to cover quite a lot of ground.