The official website of the UN General Assembly Special Session on drugs for 2016 is now available here:http://www.unodc.org/ungass2016/index.html
For now, the website does not include much information but it is worth checking it out regularly. It is also, at the moment, only available in English.
On the website, you can also access a Q&A prepared by Gilberto Gerra from UNODC ahead of this year’s Commission on Narcotic Drugs on the UN drug control conventions. It contains some interesting elements on what the conventions say with regards to harm reduction, access to essential medicines and human rights: http://www.unodc.org/documents/ungass2016//Drug_policy_provisions_from_the_international_drug_control_Conventions.pdf.
International Drug Policy Consortium will also be updating their website regularly so do have a look at that as well:http://idpc.net/policy-advocacy/the-un-general-assembly-special-session-on-drugs-ungass-2016.
Finally, Open Society Foundations have produced an UNGASS explainer which can also be of interest:http://www.opensocietyfoundations.org/explainers/what-ungass-2016