If the picture is blurry from the camera, there's nothing you can do to
clear it up.
This is not really true, but it could be quite expensive to find a program
that will do a good job -- probably not cost-effective for the average
photographer.
Picture blurring is usually caused by two errors -- out of focus (focus
blur), and motion blur. Both can be corrected to some extent, but the
process is computationally intensive, and takes a pretty sophisticted
program.
The process is called deconvolution.