What's a good site to see bid/ask walls?
btccharts.com is a better version of mtgoxlive.com - it lets you zoom out to see more price range, and has a bunch of other features.

See its forum thread for discussion of it.

Note: the site is currently down for maintenance but should be back soon.

Also, clarkmoody will show you a live updating view of the market, but the depth is shown numerically, not on a graph.