Photoshop has a "Lens Blur" filter. It has a steeper learning curve than many of the other filters, but essentially it allows you to mask your main subject, and then apply a blur that mimics that produced by your lens. You have control over the "number of blades" in the iris, and how circular or not the bokeh is. You can also control the strength of the effect and other parameters. If you take time to use it right it is much more convincing than the Gaussian blur.
Of course, I *always* get just what I want in the camera, so I have little use for the Lens Blur filter. (Just kidding!)
