Probably the easiest way to do any DC motor control from a microcontroller is to use an H-Bridge circuit.
You can buy H Bridges as integrated circuits or breakout boards, although if all you need is 80mA you're going to be going into overkill mode by buying one :-P
However, if you're going to be doing other projects with bigger motors, it's always good to have a few. I use these: http://parts.digikey.com/1/parts/577889-ic-h-bridge-5a-dc-motor-to220-7-tle5206-2.html
although there are a ton of others around.
If you want to play with circuits, though, an H-Bridge is only 4 transistors and some diodes. Just be sure you're choosing the right transistors (this is...sadly something I don't know how to do, but am interested in learning).
Keep one thing in mind, though: if you're using an H Bridge like the one I just showed you, you have to use TWO PWM outputs, not just one. If you modify it with a bit of logic circuitry, you can only use one PWM and one digital IO pin (not in PWM mode, just on/off). This is because you need to be able to set the direction of motor as well as its speed.