FOAM or #FOAMed stands for Free Open Access Medical eduation. The term was coined by Mike Cadogan, an emergency physician from Perth, over a pint of Guinness at a conference in Dublin in 2012. The hashtag for obstetric and gynaecology FOAM is #FOAMog.
Here are some resources to learn more about it:
FOAM – Life in the Fastlane
Seduction, Hype and Evidence – FOAM as Effective Learning – Short Coats in EM