Si5351

Adafruit has a board for the Si5351A.  For 8 bucks you get a itty bity board with 3 clock outputs with a range of 8 KHz to 150 MHz.  I picked up a few to play with homebrew HF radios.  (EtherKit has a version, too.)

I am using the EtherKit library for Arduino.  It is very straight-forward and I was generating clock signals in no time.

This shows the Arduino MicroView handling a rotary encoder and the I²C to the Si5351.