Bob Hughes is putting together a remarkable timeline of DC Publishing history. It's not yet complete, but it's already worth a look.
It's not just a list of facts--there's plenty of fun snark, such as this entry from February 1993: "Green Arrow: The Wonder Year- Mike Grell screws up Green Arrow chronlogy and makes Ollie even shallower than usual. 4 issues."
You'll learn stuff too. For example, I only vaguely recall that Sarah Byam and Trevor Von Eeden did a short-lived Black Canary series.
(Thanks to Tony's Tips for the link.)