For depth of field you need to use 2.43 and use this:

http://wiki.blender.org/index.php/Manual/Compositing_Nodes_Filters#Defocus

Pay close attention to the camera settings part. Place the yellow cross where you want the focus to be.

I have some sample results here but of course people have put cooler stuff on Blenderartists and I think oodmb's egg picture uses the Defocus node.

http://l333la.googlepages.com/blenderimages