Hot Air Ballooning has always been popular in Cairns with backpackers despite the deadly 4 am start time. You can do either a 30 minute flight or a 60 minute flight and both fly over the Atherton Tablelands. It is a a 40 minute drive to the take off point on the Tablelands which has more stable weather than coastal Cairns. Make sure you take warm wear especially in winter as it can be bloody freezing. The flights take off so that you can catch dawn from the balloon.
The most popular option for a little less than $250. You get to help pack up the balloon whether you like it or not.
Spend an extra half hour in the air for just an extra $100.