Videomaker has an understandable, though perhaps overly-simplistic, summary of what DOF is to filmmakers, and includes suggestions on “cheating” a shallow depth of field look with small-sensor camcorders.

“If a shallow depth of field is something that you want to achieve, try these techniques:
*Calculate the depth of field on the shot. Either do the math, or use some of the depth of field calculators available online (see sidebar). Once this is known, adjust the setup as needed.
*Open up the aperture as wide as possible. This will shallow the depth of field, but it can also brighten the image too much. Keep some neutral density (ND) filters handy just in case.
*Mount a longer focal length lens on the camera. Screw-on lens adapters are available for many prosumer cameras. Use a telephoto lens to shallow the depth of field further.”

They also touch briefly on the principle of a Circle of Confusion, again offering a short and simple explanation. For those interested in learning more, Wikipedia has a good writeup on CoC.

(Via Videoguys)