Woops - i didn't fully read the original question!
For flights:
As Bailey suggests, use Webjet (or alternatively
http://au.skyscanner.com/ or BOTH) to determine the cheapest flight option over, then go direct to the airlines website and book from there.
Stick with Qantas / Jetstar / Virgin. DON'T fly tiger - there's no guarentee you'll get there (even if they get back in the air post this "grounding" business which they are currently embroiled in)!
For accommodation:
Best is to have a good mate over there to stay with (like i will be doing for this show) - accommodation cost = Carton
Failing that:
Use these websites to scope out various accommodation options:
www.expedia.com.auwww.hostelworld.comhttp://www.wotif.com/From time to time, hotels do deals and/or have reduced rates if you stay for more than 3 days at a time or so. Find something you think is ok then go here to check other travellers reviews of the joint:
www.tripadvisor.com.auMy general rule is that cheapest is not always best - why save $10 a night to stay in an utter shithole when you can pay just a little bit more and stay somewhere ok / decent?!
I wouldn't go for the bog-standard "flight and hotel" package offered by travel agents like flight centre. From what i understand they don't make much $ in the booking of flights etc - the $ for them is in the hotel references / bookings as they will always suggest you stay at a hotel that they are affiliated with (and thus get kickbacks from for doing so). You will want to scope out your accommodation yourself as well as the hotel that they suggest may be MILES from the gig etc so you have to factor in travel costs (taxis etc). The best choice is to stay somewhere both close to the gig AND central or a happy medium...
Bear in mind that the knucklehead promoters of this gig have put it on the SAME WEEKEND AS THE AFL GRAND FINAL, so i wouldn't dally regarding organising accommodation or flights. When i booked (flights) a month ago, ALL the cheap tickets were gone - there were only a handful of medium price (which i used a HEAP of frequent fliers to offset the cost of) and of course plenty of full fare / business seats available. Expect to pay $400 - $800 return!!
And for good reference metal reference:
http://www.metaltravelguide.com/oceania/australia/victoria/melbourne/TCHUSS!