Some Cams affiliated clubs are into the "social" side of things eg brunch, drive-in movies, bbq's, etc. Others are into competitive events (motokhana, supersprints, drifting, rallying, etc) and others are into cruising.
Go to the CAMS website
http://www.cams.com.au/Sport/Club%20...%20Finder.aspx and check out the clubs listed. You should be able to filter on "speed" if you want to compete in motorsports. Then just check the calendar of the club's website and see if they have the events you are interested in.