I am aware of the blur options in the compositing nodes and was wondering if there were a way to blur just parts of the picture to make it seem farther away than the closer parts?
Use the DOF node.
to artificially do it, you have to feed a mask to the Factor input (if there is one) to tell it to blur an area more than another, or mix the two (original and blurred) feeding the mask to the Fac input of the mix node. See my tutorial on Blur the Background in the wiki, compositing section.