Studio Astarte - a Melbourne stamp company run by Stacey Apeitos, who creates amazing stamps and has great ideas for using them. Stacey makes polymer stamps that are "sticky" on the back - "Jellies" - use them mounted or unmounted.
My Stamps - Another Melbourne stamp company, run by Cathy Daulman. Cathy designs and makes her own stamps, also in polymer form.
Krafty Lady - a Melbourne (well, actually Dandenong) stamp company run by Kristine Lockwood (K.L. - Krafty Lady - get it?). Tons of stamps, unique art moulds.
Paperific Craft Expos - The best paper shows in Australia, especially Melbourne Paperific!
Stampmania Australia - Moya and Leanne Scadden run this company in Perth. They sell a great range stamps, with lots of mail art and collage ideas, some trees that I have used a lot, and a helicopter that is very popular with my sons!
SERS - My favourite stamp club, South Eastern Region Stampers (YAY!). If you live in the eastern part of Melbourne, this is the place to be on the last Saturday of the month.....