Variety calls it "an A-1 entry at the b.o." It's on Roger Ebert's list of great movies. Senses of Cinema explores context. Bright Lights Film Journal deals with the film as propaganda. FilmReference.com has an article. The New York Times ends its review by saying,
In short, we will say that "Casablanca" is one of the year's most exciting and trenchant films. It certainly won't make Vichy happy—but that's just another point for it.
11/28/2009: Out of the Past has a round-up of favorite bloggers' posts on the film.