(Latest edit @ 0915 - I'm not going to be near a computer again until tomorrow, so keep up with the latest info on National Radio and the rest of the internet will provide.)
I've just received notification of a magnitude 7.4 (revised to 7.1) quake centred 30km west of Christchurch, and 33km down, and Facebook updates from friends down there are indicating things like power outages (someone is reporting transformers blowing, and power is out in most of rural Canterbury), and broken pipes (including sewer & water mains), cracked swimming pools, things thrown off shelves, toppled furniture, chimneys and walls down, structural damage, and aftershocks keep happening.
Reports that people had self-evacuated from shoreside suburbs in case of tsunami - which is exactly what we tell people to do in a large local quake. Fortunately with the quake being centred on land, it doesn't appear to have generated any - but you don't know that at the time, and you shouldn't wait around to find out.
Some images appearing online of damage to unreinforced masonry & shop facades, and the entire brick side of someone's house, many streets are blocked by debris, and some roads have been damaged by ground spreading, probably due to liquefaction. The airport is currently closed while they check the runways, same for South Island rail until the lines are checked.
Minor injuries are now being reported - I'd guess a good number will be people cutting their feet on broken glass or china as they tried to find a torch in the dark.
Updates to Facebook & Twitter from people's mobile phones are a useful source of information - and a good way of finding that your friends are okay!
http://www.weather.gov/ptwc/text.php?id=pacific.2010.09.03.164512 - The first notification I received was a text forwarding the PTWC tsunami bulletin at about , saying that there was no tsunami threat - didn't feel the quake at all. I only get a text for that if NZ is involved, so I revved up the laptop to find out the story, and the Geonet report came in shortly after.
0710 - Christchurch Mayor Bob Parker giving a textbook perfect interview on National Radio - good factual information & key messages. Was also good to hear the Sting played earlier, followed by official emergency messages.
Major damage to the sewerage network, so people are advised to not flush their toilets, even if they still have water.