Just (ca 20:50/8.50 pm) experienced my first earthquake (South-eastern suburbs) -- or rather earth tremor. Rattling doors, a bit of noise, a bit of shaking. Felt like about 10-15 s. More exciting than scary, although I would NOT have wanted to be any closer to the epicentre than we already were (100 km).
Funny it should happen in Australia after five years in California without the slightest tremor.
I like the possum comment below -- was my first thought too! The second one was wind.
If you felt it, you can report it here http://earthquake.usgs.gov/earthquakes/eventpage/usb000ajek#dyfi
There is a point in reporting your experience, since earthquakes aren't just reported in terms of the energy released, but also in terms of damage (or perception).
Update 22:02: http://www.seis.com.au/ is slowly coming back online, but there's no obvious information up yet.
http://www.seis.com.au/ and http://www.ga.gov.au/earthquakes/ went down immediately, and the ga.gov.au site is still down. www.seis.com.au is operating slowly.
Update 21:52. ABC 24 is covering it right now. Quake happened 7 minutes to 9 with the epicentre over by Trafalgar near Moe. No serious injuries. Upgraded to M 5.5.
Update 21:30
The news sites are catching up:
http://www.abc.net.au/news/2012-06-19/magnitude-52-quake-shakes-southern-vic/4080446
http://news.smh.com.au/breaking-news-national/melbourne-hit-by-earthquake-20120619-20m8d.html
http://www.heraldsun.com.au/news/more-news/strong-tremors-rock-victoria/story-fn7x8me2-1226401623358
http://www.theage.com.au/victoria/quake-shakes-melbourne-20120619-20m88.html
Update 21.27: ABC 24 just confirmed it. M 5.2. Moe was the epicentre.
Update 21.10: It's on the USGS website: http://earthquake.usgs.gov/earthquakes/eventpage/usb000ajek#summary
Apparently it was a Magnitude 5.2 centerd somewhere out in Gippsland. Best guess at time is 20:53:29.
The magnitude will likely be adjusted once local data is available.
Postscript:
I posted since the seismology sites were down and there was nothing on the news. Apparently I wasn't the only one who was looking for information: