Both the Royal Australian Mint and the
Perth Mint have released many over the years in conjunction with Australia Post. There are also many unofficial issues, some of which were made by Nuphil. You need to be very careful with most unofficial issues as you will simply be throwing away your money, Nuphil is an exception to that rule.
All the official Australian issues are listed in Greg McDonalds Guide to Australian Coins and Banknotes.
They can also be found here.
http://www.australian-threepence.co...-covers.html