Go to your local outdoor gear store and buy the high strength finger grip exercise gadget for climbers.
http://www.amazon.com/Gripmaster-Exe...289973-8969700
Start carrying it around with you and using it all the time. I think some guitar centers sell them as well.
Try some of the following hand stretching exercises:
Hold your hand vertical palm facing away with your fingers flat. Do the "V" shape (star trek), then switch to three fingers to one side and one to the other side. Go back and forth.
Hold your hand vertical palm facing away with your fingers flat. Starting with your index finger, bend it down from the knuckle, just your index finger. Once you can do this without moving your other fingers, move to your middle finger. Once you can do that one without moving your other fingers, move to your ring finger. Finally, when you can do that, do it with pinkie. You will likely feel a tightness in your pinky at first when your doing this, right around when it is at a 90 degree angle to your hand. But trust me, it will pay dividends once your stretch it out. Obviously stop if you feel any pain and take your time with it.
These two exercises will help to further seperate and strengthen your fingers, but you will be able to tell the most difference with the pinky. The knuckle bend exercise will stretch out the ligaments in your hand as well as the ones that provide all your fingers power which reside in your forearm. The V exercise will help to strengthen the side to side muscles in your hand between your fingers as well as stretching them. Do these exercises or like 3-5 minutes each and rock one of those gripmasters, and you will notice a difference pretty quick. Another easy exercise is to ball up an entire newspaper one sheet and a time with one hand.
Other than that, just devise exercises for your self that take place in a 4 fret span and make sure to not move your hand and take one fret per finger. Heres a simple one I came up with to go down the neck which is good for your pinky and string skipping.
G-----------------10---9---------------9----8
D-----12---13-------------11---12-----------
A-----------------------------------------------
E--10---11----13---12--9---10-----12--11--
and so on all the way down the neck and then back up.
You do the first three octave in one hand position then shift down on fret to do the 4th octave with your pinky and index finger. Then you repeat the same pattern from there, shift down a fret after three octaves, and repeat. Focus on keeping your hand open and your fingers arch. Don't worry about it when your pinky inevitably curls up or acts funky, just correct it and stay focused and comfortable. Believe it or not I have the opposite problem where my pinky pulls back away from the fret board and straightens out too much when I am playing quickly or in certain positions. I do the same exercises now to work on keeping it arched above the fret, though at one time I had the same problem you describe.
hope this helps in some way
good luck