Australian Sites:
www.bigkid.com.au - Gaming news and reviews.
www.aussiegamer.com - "the all australian gaming and hardware site"
Dan's Data - Hardware reviews. Well-written and very funny in places.
ng-online.qgl.org/ - nG! online - quake-oriented site, the social side of the scene
Steve's Corner of the WWW - hardware reviews and news

News / Info Sites:
www.hardocp.com - Excellent, daily-updated overclocking info site with attitude. :)
www.arstechnica.com - Very technical site - excellent articles.
www.anandtech.com - long-standing, very good technical site.
www.slashdot.org - community geeknews site
www.shugashack.com - games geeknews site
www.unlimitedhardware.com - John Bogush's great overclocking and hardware site.
www.overclockers.com - Good info, CPU results database. (we're not affiliated in any way)
www.thetechzone.com - lots of technical info.
www.overclockin.com - reviews and lots of news daily.
www.theregister.co.uk - cpu and industry news
www.overclockers.co.uk - british news and review site, sells parts across europe
optimize.bhcom1.com - the high-performance PC guide
www.bxboards.com - excellent motherboard info site
www.hardwarecentral.com - commercial site with lots of info
Overclockers Workbench - good site, comparos and reviews
www.planethardware.com - news and hardware reviews
DimensionX - LOTS of links to news and reviews. A "portal" of sorts.
www.AGNHardware.com - news, reviews and how-to's
www.hardwarehq.net - NZ-based hardware news site
www.amdzone.co.uk - British AMD info site

Cooling Info:
www.electronics-cooling.com - Homepage for the engineering magazine of the same name. They have an archive of articles - there is a serious amount of very technical info here. Great site.
www.tellurex.com - manufacturers of TEC (Peltier) devices. Lots of info on their site including an excellent FAQ. A little biased towards their products, of course, but still a great resource.
www.agaweb.com/coolcpu - info on watercooling CPU's
www.heatsink-guide.com - guess what they do? :)

Extreme Rigs:
www.frostyfox.com - quality setup, amazing results and a lot of good info.
Dr Ffreeze - probably the most [in]famous, results not all that impressive though..
Orthello - C400, water-cooled, peltiers etc from New Zealand - nice rig!

Downloads:
Desktop Creations - Al's awesome wallpaper for your overclocked PC.
MBM - Excellent motherboard monitor. Temps, fans, speeds, voltages, the lot!
H-Oda - Homepage for WCPUID (cpu info program - very useful) and SOFTFSB (change FSB on the fly under windows)
Sandra - Great benchmarking / sysinfo program.
www.tweakfiles.com - lots of hardware files in one place, plus hardware news
iwarp downloads - files files files, run by an Aussie..

Feel free to suggest links.