My project would not be possible with out the hard work and extreme dedication of these people and those who support them.

Teensy 3.1 and Teensy-LC. Thank you Paul Stoffregen!
pjrc.com
github.com/PaulStoffregen

USB Host Shield Mini. Thank you Oleg Mazurov!
circuitsathome.com
github.com/felis

Also xxxajk (Andrew J. Kroll) wrote spi4teensy3, Thank you!
github.com/xxxajk/spi4teensy3

Paul Stoffregen also has a forum for project help, loaded with great information like this Teensy Quick Reference: Code Examples, Tips and Tricks.

Oleg Mazurov wrote an awesome series of articles that go over the basics of USB report descriptors and HID.

Visualizing HID device reports and report descriptors:
A simple introduction to USB interface and report descriptors.
https://www.circuitsathome.com/mcu/usb/visualizing-hid-device-reports-and-report-descriptors

HID support for USB Host Shield Library 2.0 released:
Interfacing to HID boot protocol devices.
https://www.circuitsathome.com/mcu/hid-support-for-usb-host-shield-library-2-0-released

Arduino USB host Articles:
Arduino USB host – Communicating with HID Devices
https://www.circuitsathome.com/communicating-arduino-with-hid-devices-part-1

Arduino USB host – Pre-prototyping – Part 1
https://www.circuitsathome.com/mcu/programming/arduino-usb-host

Arduino USB host – First programs – Part 2
https://www.circuitsathome.com/mcu/arduino-usb-host-part-2-classes

Arduino USB Host – USB Descriptors – Part 3
https://www.circuitsathome.com/mcu/arduino-usb-host-part-3-descriptors

Arduino USB Host – Peripherals – Part 4
https://www.circuitsathome.com/mcu/arduino-usb-host-part-4-peripherals

Lightweight USB Host Articles:
Lightweight USB Host. Part 1 – Motivation
https://www.circuitsathome.com/mcu/lightweight-usb-hostpart-1

Lightweight USB Host. Part 2 – Hardware
https://www.circuitsathome.com/mcu/lightweight-usb-host-part-2

Lightweight USB Host. Part 3 – accessing MAX3421E
https://www.circuitsathome.com/mcu/lightweight-usb-host-part-3

Lightweight USB Host. Part 4 – The code
https://www.circuitsathome.com/mcu/lightweight-usb-host-part-4-the-code-repository

Lightweight USB Host. Part 5 – control transfers
https://www.circuitsathome.com/mcu/lightweight-usb-host-part-5-control-transfers

Lightweight USB host. Part 6 – introduction to HID
https://www.circuitsathome.com/mcu/lightweight-usb-host-part-6-hid

Other Links:

Circuits@Home.com USB Host Shield References

USB Host Shield Projects: A summary and Links for Hardware information, Arduino Libraries, and Application-specific information
https://www.circuitsathome.com/arduino_usb_host_shield_projects

USB Shield Blog: Some are older articles not used here, but have valuable information.
https://www.circuitsathome.com/category/mcu/arduino/usb-shield

Hardware Manual with Pictures of how to hook up the hardware!

• Layout (Pinout descriptions)
• Basic Usage
• Power Options (3v & 5v limitations)

https://www.circuitsathome.com/usb-host-shield-hardware-manual
(Compare with Teensy 3.1 “USB Host Shield Library” below.)

Teensy 3.1 USB Development Board References

Teensy 3.1 – Main Page: New Features, Technical Specifications, and Pinout Diagrams.
http://www.pjrc.com/teensy/teensy31.html

Teensyduino
Teensyduino is a software add-on for the Arduino IDE software.
http://www.pjrc.com/teensy/teensyduino.html
Also see
https://forum.pjrc.com/threads/28207-Arduino-1-6-2-support

Download the Arduino Software
http://www.arduino.cc/en/Main/Software

Download Teensyduino
http://www.pjrc.com/teensy/td_download.html

Teensy 3.0 now supported by the USB Host library: 3.1 support and pinouts!
https://www.circuitsathome.com/mcu/teensy-3-0-now-supported-by-the-usb-host-library

USB Host Shield Library with Pictures of how to hook up the hardware!

• Hardware Requirements
• USB Host Capacitance
• USB Host Power Voltage (Power requirements for all devices)

http://www.pjrc.com/teensy/td_libs_USBHostShield.html
(Compare with USB Host Shield “Hardware Manual” above.)

Teensy 3.x Native USB Host Preview Available 3-24-2015
Looks like something else to play with.
https://forum.pjrc.com/threads/28173-Teensy-3-x-NATIVE-USB-HOST-PREVIEW-AVAILABLE

Digital I/O
http://www.pjrc.com/teensy/td_digital.html

USB Serial
http://www.pjrc.com/teensy/td_serial.html

USB Keyboard
http://www.pjrc.com/teensy/td_keyboard.html

USB Mouse
http://www.pjrc.com/teensy/td_mouse.html

SPI Library
http://www.pjrc.com/teensy/td_libs_SPI.html