+1 to everyone saying the d40 is an excellent camera. I shoot semi-pro freelance with a d70 -- now outdated compared to the d40 -- with superb results, and the d40 should not limit you at all.
I swear by the writings and reviews of Ken Rockwell. You can read his review of the d40 here:
http://www.kenrockwell.com/nikon/d40.htm
As he states, your gear doesn't matter. It is all in your abilities as a photographer, which involves your ability to "see" a picture, and then your understanding of the physics of photography and how that translates through your camera's settings onto film/memory cards.
Get yourself the d40 and use the money you saved over a d80/d200 to get yourself the Nikon 18-200 VR. You'll be set!
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E90 335i, black sapphire metallic, terra dakota, PP, SP, 6MT, cold weather, iPod, CA, burl walnut, LeatherZ ZHP shift knob, 19" M5 reps w/ Kumho Ecsta SPT staggered, BMC drop-in, SSTT. Amen.