Teensy 2.0, LC, 3.x, 4.x core libraries for Arduino.
The latest stable version of Teensy's core library is always available in the Teensyduino installer, at this page:
http://www.pjrc.com/teensy/td_download.html
(This fork adds PS4 controller emulation support for Teensy 3.x/LC support. Use with RDS4Reboot.)