Other useful websites
http://www.ibunity.com/
Made by a bunch of IB survivors, experts in selected subjects and giving feedback on essays.
http://www.ibscrewed.org/
“We provide free educational materials for International Baccalaureate diploma students, including notes, online tutorials and study support.”
http://freeexampapers.com/#/IB
Lots of exam papers for all the IB subjects.
https://www.osc-ib.com/revision-centre
Free Maths HL & SL video tutorials.
http://www.ibsurvival.com/
Great for discussion but you have to pay to become a member.