Hey, I'm one of Haggis's friends who lives in Chch :) (hi haggis!)
OK so the indoor options have been covered by timfreddo.
As for real rock bouldering, the nearest to the city is Albert's Terrace (at the base of the Port Hills) which has a few problems and a small sport crag. Otherwise you have to go up into the Port Hills and see what you can find at the crags. I think the guidebook has a bit about bouldering but the area's not exactly renowned for it! If you're keen to train on sports routes there's some great ones at Britten Crag and steep stuff at the Cave.
I've heard there's some good deep water soloing out at Talyor's Mistake if you're interested in that.
My partner Tim's unemployed at the moment so if you want a local to show you around or do routes with give him a shout -he's away for a couple of weeks at the moment but I'll tell him to check out this forum when he gets back.