Any type of chromatic, 4-fingers-per-string excercise is a good start. If you find yourself consistently practicing scales, you will notice that it's only a matter of time before you will start using your pinky finger.
For that matter, it doesn't necessarily need to be scale/solo-type stuff. You can also excercise your pinky finger with chords, especially jazz voicings. Some of those intricate, odd chordal arrangements can really enhance the usage of all your fretting fingers. I'd post some irregular voicings for you to try, but I'm not currently near a guitar and that simply requires too much thinking to tab stuff without a guitar handy. Lol.
Hope some of those ideas set you on the right track,
Matt