http://www.lifehacker.com.au/2011/04/lifehacker%E2%80%99s-20…
Lifehacker has got a great guide to getting to your major capitol city's airport. I can only speak for Melbourne and there's a couple of things that should be added.
Melbourne:
Never tried taking the public bus. Anyone every tried this?
Taxi- Usually around $50 from the city, so if you have 2+ people it's probably cheaper doing this.
Airport Shuttle-These are quite big in the US. Have taken SuperShuttle at a number of US airports. Googling around leads me to http://www.vhaairportshuttle.com.au/. $16pp pickup from city and nearby suburbs.
Can't remember where I heard this tip but if you want to short term park for the day, you can try parking in the McDonald's parking lot.
Creeps whilst travelling, crossing line?
Just putting it out there
I've personally never had any creep-y experiences with public transport(bus)