Far North QLD:
Cape Tribulation! If you go with a guided tour make sure you stay overnight, it's a very stressful day otherwise and the Cape is well worth being enjoyed!
Quite a few things you can do around there: horse riding (expensive),fruit tasting, swimming holes...
A nice hostel to stay at is Aussie Way Backpackers (doubles are $68 a night)!
If you wanna party in Brissie got to the VIC on Thursdays, to the Valley on Fridays and Saturdays, to the Normanby or the Fox on Sundays and to Down Under Bar from Monday to Wednesday!
Truely a gem for me and easily accessible from Brisbane and the Gold Coast! From June on a good place to do landbased Whale Watching! A very quiet island. Don't expect party. Go there to hike and to enjoy the nature! Bring some food, cause it is expensive on the island. Dining out is affordable though at some places.
Stay at the YHA or search on Tripadvisor for a nice B&B
Byron Bay Hinterland:
Don't miss out the Hinterland in Byron Bay, especially if you have your own transport! Nimbin is not special, but the nature in the area around is stunning!
If you can afford spending a lot of money on a special accomodation try Silk Pavilions at Mount Burrell! The offer Glamping and this place is so special and beautiful. Situated between Nimbin and Uki.
Otherwise Wwoofing will be easy in this area.
Places to visit are the Channon Markets, Murwillumbah, Uki, Mooball etc.
The Rainbow Region will make it easy for you to get in touch with locals!
Hope I could help you! :-)