Update 11 for Revit 2015 R2:
http://up.autodesk.com/2015/RVT/Autodesk_Revit_2015_R2-x64_Update11.exe
Readme: http://up.autodesk.com/2015/RVT/Autodesk_Revit_2015_R2_UR11_Readme.htm
Enhancements: http://revit.downloads.autodesk.com/download/2015RVT_RTM/UR11/Enhancements_List_RVT_2015_UR11_forR2.pdf
Update 11 for Revit Architecture 2015:
http://up.autodesk.com/2015/REVIT/Autodesk_Revit_Architecture_2015-x64_Update11.exe
Update 11 for Revit LT 2015:
http://up.autodesk.com/2015/RVTLT/Autodesk_Revit_LT_2015-x64_Update11.exe
Update 11 for Revit Structure 2015:
http://up.autodesk.com/2015/REVITST/Autodesk_Revit_Structure_2015-x64_Update11.exe
As per this tweet, you can find it on your Autodesk Account under Product Updates: