I wrote a .PDF tutorial on the Lens Blur filter that has a focus on creating Depth Maps. A basic linear and radial gradient works with many photographs. The Quick Selection tool can be used for more complicated Depth Maps.
If you've wanted to use the Lens Blur filter to reduce DOF without giving your photograph an artificial appearance, this tutorial will get you started.
Don't let the title scare you. Lens Blur has been around since Photoshop CS. You can add a realistic bokeh effect with versions of Photoshop prior to CS4. http://www.thelightsright.com/Reduci...thPhotoshopCS4
Enjoy! As with my other tutorials, this is free to all!