I've used Reddit (you can advertise on specific subreddits such as /r/australia) and StumbleUpon. If you go the Reddit route, don't use an annoying amount of fluff words in the post title. That'll make 'em upset.
Hey thanks! I haven't got any experience with reddit but I have heard that you can upset them easily. I will look at some of the other posts to get an idea of what is suitable.
StumbleUpon is a great idea! I used to use that all the time. Didn't cross my mind to use it. Thanks