Two stamps on bubble mailers ($1.20).
I send cards in a 100mm x 180mm bubble mailer and as long as the thickness is below 20cm they are $1.20 to send. They are classed as a 'Large letter".
Its one 60c stamp if the 'letter' is less than 5mm think, which rules out bubble mailers.
I also heard there was a rise to 70c stamps as of July 1st, but i bought a roll of stamps the other day and they were the 60c ones. Not sure what the go is.