Description
You would figure that creating simple on/off pulses is a pretty easy thing. Well it is. Watch: On....off.....On.....On..(DANG). Ok, it's pretty simple for a single signal, but if you're wanting to create a bunch of well-timed on/off signals, that gets particularly tricky, even for an Arduino.
Enter the PCA9685, and its breakout board from Adafruit.
Instead of using up your limited number of PWM lines, or trying to fake it all in software (and using up all the resources on your microcontroller), you can simply pop a signal over to this chip via I2C to tell it which of 16 lines you want to pulse, with 12-bit (4096) levels of accuracy. And it'll keep doing it, all by itself. Pretty handy. And the PCA9685 can be chained 62 deep, for a total number of control of 992 PWM output lines - that's impressive!
The kit comes mostly assembled, with a set of 3x4 headers for installation of servo/LED plugs, a 2-pin power terminal block, and a 6-pin 0.1" header for breadboard-compatibility.
Features
 Power input via terminal block or 0.1" spaced pins
 Terminal block has reverse-polarity power input protection
    Green power LED
    3-pin connectors in groups of four for easy 16-servo installations
    Easy chaining of boards
    Power filtration capacitor installation pads
    220Ohm output line projection resistors
    Solder pad jumpers for address selection
Specifications
 5V compliant, and still talks to a 3.3V microcontroller.
6 "address select" pins for configuring up to 62 ICs on a single I2C bus
    PWM frequency adjustable up to approximately 1.6kHz
    12-bit frequency resolution (equates to about 4µs resolution at 60Hz refresh rate)
    Configurable as push-pull or open-drain output
    Output enable pin available for outside-the-microcontroller "shut it down!" control.

Dimensions
 No headers or terminal block) 2.5" x 1" x 0.1" (62.5mm x 25.4mm x 3mm)
 Weight (no headers or terminal block): 5.5g
Weight (with 3x4 headers & terminal block): 9g
This product comes with a fully tested and assembled breakout as well as 4 pieces of 3x4 male straight header (for servo/LED plugs), a 2-pin terminal block (for power) and a piece of 6-pin 0.1" header (to plug into a breadboard). A little light soldering will be required to assemble and customize the board by attaching the desired headers but it is a 15 minute task that even a beginner can do.