Currently I am working hard to get my Trigonometry content converted to mobile friendly formatting in the new content system.  Lots of issues but I am making progress.

https://ens-textbooksystem.appspot.com/

http://www.opengraphingcalculator.com/

http://www.openalgebra.com/

http://www.opentrigonometry.com/

http://www.trigcheatsheet.com/

I need to plan a complete overhaul of these offerings at some point!