http://www.qld.gov.au/floods/donate.html
Joint appeal from Red Cross, the Salvation Army and the Queensland Emergency Service, I believe.
Edit: http://telethon.smartservice.qld.gov.au/ takes you directly to the credit card donations page. First link gives you other options.
Edit 2: Red Cross direct donations: https://www.redcross.org.au/Donations/onlineDonations.asp
Salvos: https://www.salvationarmy.com.au/newdonation/donation.aspx