As is evident from the quality of the photograph I hereby present, I am not a Pro. Heck. I don't even come close to my 5th grade cousin.
But I am OK with my favourite photo editor GIMP. So I tried developing a technique similar to the Unsharp Mask filter. All out of trial and error, so I don't guaranty anything. I have noticed it only reduces soft motion blur. So take a backup of the images you try this on. You have been warned.
( I found that the steps apply much better to the following images :
So here goes nothing.
Select your camera shake affected photograph and move on to the next step.
Step 1: Measure the Blur.
Step 2: Triplicate the Layer.
Don't ask me exactly how I came up with this. It was a bit of looking in the code of "unsharp mask" filter and a lot of trial and error.
Step 3: Add Motion Blur.
For people who did not catch the above, it is simple : We fight motion blur with more motion blur, kind of like fighting fire with fire. Now on to what we do in this step.
In step 1, we measured the motion blur. Use this to fill the parameters for filters>blur>motion blur. Make sure you do this for the top layer. You may have to add or subtract a multiple of 90 to create the right motion blur.
Experimenting is a nice productive time pass. Do it.
Step 4: Switch Top Layer Mode to Grain Extract.
Step 5: Merge the Top 2 Layers.
Step 6: "Grain Merge" the Resultant Layer.
Play with Colors>Levels and the opacity of the layer to your liking. After each unblurring, if more is left, repeat. The resulting image is a bit sharper than the original.
The effect depends on different qualities of blurring, both during the shoot and step 3.
Your mileage may vary. Inputs are very much welcome.