Jes,
I havn't been everywhere on the east coast but I'll give you some suggestions on where I've been and what I've done!
In melbourne I'd recomend base in st kilda.. very modern place, a bit lacking on the character department, but a lot of fun as there are lots of young people there!
I'd recomend making a stop-off at newcastle on your way north.. newcastle is about 2hrs north of sydney. the newcastle yha is very cool and they round everyone up for a free meal in a local pub most nights which is a great ice breaker!
apparently there is a new yha opening on the coffs esplanade.. that might be worth checking out if you stay in coffs harbour.
in brisbane i'd recomend staying at either 'the palace' or at 'bunk'. the palace is an old-style backpackers in a rambling old building full of character.. it's also in the city which is going a little out of fashion. bunk is kind of like base, in that it's a modern backpackers lacking character but full of lots of young people having an awesome time. the bar attached to bunk, birdee num num's, is an awesome night out. bunk is in fortitude valley (about 10mins walk from the palace), but the pubs/bars/clubs in the valley are generally more trendy than those in the city.
i'd recomend making a trip over to fraser island if you can.. it's an awesome spot! i'm not sure about hostels there but apparently there is a yha?
i'd definitely stay halse lodge in noosa too!! noosa is great - you *have* to walk through the national park.. but be warned that alexandria bay is a nude beach and it's often full of oldies, so don't plan on spending too long there!
finally, in cairns i'd recomend gilligans. again, it's in the base/bunk style of modern-lacking-character-but-lots-of-fun. i figure on a trip up the coast you'll stay at lots of 'character' places so don't let the moderness of the new places put you off.. that said, if you spend a night out on the town you'll probably end up at the bars attached to the modern backpackers.. so you'll see a bit of the place anyway.
enjoy your trip, it's great!! if you want more advice/whatever drop me an email -
danboman@gmail.com