Depending on the size of the object, good old Australia Post does remarkably well (I think)...
We use TNT at work for all of our sample shipments...they seem to go okay and do a nice job (at least for us) keeping stuff on time and intact...the records of movement (tracking of packages) are important to us too as some of our stuff is still "top secret experimental"...
Most couriers are a pain for casual one offs and charge more without an account. In 15yrs of daily use, the good ol aust post has never lost any shipment, and the $8 express post bag max 3Kg goes anywhere. Express can be a tad pricy for heavy stuff priced on the scales (if it dont fit in the 3kg bag), but if you dont mind a delay, normal post is good, resgistered is advisable so you can track it.
Aus post is ok for under 20kg. I have booked using Airroad, was very painless. And you dont need to register to get a quote. Lets see how they go.
I have been happy with aus post for smaller stuff.
TNT only to same day for one offs and its expensive unless you have company account. Startrack dont do one offs.
