I do second Batman: Black and White! I just got one of the trades today! *flails* They're not all good, but what I like them for is they're nibble-sized and you can stop after each one and say "Did I like that story? Did I like the art?" and start noticing what things you like and don't like. Very nice for developing your sense of Batman. :)

Superman trades, uh. A lot of them are terrible! Mina mentioned all my favorites (and if you don't read All-STar Superman soon, I shall die!)

Godfall makes no sense, but is very pretty.

Have you read Kingdom Come yet? I think you'd like it...

You have read all of the Loeb run of Superman/Batman, right?

"Camelot Falls" and "Up Up and Away" are two recent Superman runs that were pretty good, from what I saw.

That's about all I've got so far! :)