I just found this great Batgirl/Oracle site:
It has lots of information, both historically and on the current continuity, and it lists the comics the information is from and points out contradictory and retconned continuity.
Once you're over the (not really necessary) Flash introduction on this site it has also lots of information on Oracle and Black Canary:
Among many other things it has character biographies and extensive lists on collecting Batgirl, Oracle and Black Canary, and also reviews of many comic books.
Speaking of resource sites, does anyone know what happened to The Unofficial Guide to the DC Universe? It was at http://www.comicboards.com/dcguide/ but there seems to be some restructuring going on at the http://www.comicboards.com/ site.