Hotmail is Australia's most popular email service. MSN Messenger was the most popular IM service, though the users are now split into MSN Messenger and Windows Live Messenger, but if you count the two as one; it's on top.
I use Gmail, nice interface. I don't like Google having all of my web searches
and emails, but Gmail is too convenient (I don't sign up for other Google stuff though, and I use separate domains for email and search). I have a Windows Live Mail account, but it's too inconvenient because it's not browser-independant.
Optus is a shit ISP as well. I guess that Bigpond could be called the Aussie AOL, but the real AOL is here as well, and Bigpond doesn't have crappy software bundles, just crappy internet access.
PS the best Aussie ISP is Exetel
.