Routine screening is recommended for those over 50, but can (and should in many cases) be done once you are over 40.
I have made my appointment: you should too.
Australia
http://www.breastscreen.org.au/
UK
http://www.cancerscreening.nhs.uk/
Ireland
http://www.breastcheck.ie/
USA
http://www.breastcancer.org/testing_mamm_where.html