In reply to puppythedog:
The three major walls you haven't been to are Mile End, The Castle and The Biscuit Factory/Arch.
The Biscuit is bouldering only, and ME has only a very small roped area and lots of good bouldering.
I haven't been to Castle, but it apparently has a mix of lots of ropes and bouldering.
If I was going to 'make a day of it', I would choose Mile End for its sheer variety, size and old-school vibe, but that's a very personal thing, and it doesn't give you much in the way of top-roping potential.