Postcrossing is very well organised, I'm impressed with how they run it. I joined 22 March so no stats for me for March as nothing got registered having taken 24 days for my first postcard to arrive at its destination which was Russia. I received my first postcard on the 27 March which went to Germany.
There are 5638 (as of 24 May 2015) members in Australia who have collectively sent 387,789 postcards so far (that is a lot of postcards keeping the postal service economy going). Our postal service is run by Australia Post. Australia has received 395,078 postcards. Australia ranks 17th in the postcrossing world.