Try doing the spider exercises at
http://www.melbay.com/guitarsessions/jan06/flat.asp although it is for flatpicking, it will help with starting to use that pinky and stretching the fingers of the fretting hand. As Fretsource mentioned, practise the chromatic scale (a lot), that will also help. The pinky is a very handy finger especially on the faster pieces, but my playing partner has the same problem and he gets along fine without using it, but it always looks akward to me when he plays and shifts his hand all over the place where he could just be using his pinky to get the note easier. You could also practise your normal scales and force yourself to play one finger per fret.
Good luck