A few years ago we went to the Kidstown Adventure Playground near Shepparton in Victoria. It is an amazing (huge) community built play ground that is a great example of community engagement.
It was an initiative of community members and has relied on community support for its development. Now it is a great community resource that is used by a wide range of groups, is major tourist attraction and is heaps of fun.
It really shows what can be done by a group of dedicated people.