I just finished porting Eberhard Fahle’s LedControl library for controlling the MAX7219/MAX7221 with an 8x8 LED Matrix or 7-Segment displays. The port was very minor. The wiring was the ‘fun’ part. Spend the extra bucks and buy one of the backpacks!
It is registered as a library in the IDE and can also be found here: https://github.com/chrisloris/LedControl-MAX7219-MAX7221.