Update 2008-02-27: The rumours are true! Here’s the site for the modification. Sounds doable if you are handy with a soldering iron and don’t care squat about your camera’s warranty.
Basically you hardwire a lens chip to you camera and turn it on to fool the camera into thinking you have a chipped lens. Before exposure the chip is activated, and the camera meters.
Original post follows:
There are rumours that someone has found a way to get the Nikon D40 to meter with manual lenses. Here’s the dpreview.com post.
If this turns out to be true, and not too expensive, it will definitely be something for me. I’ve recently purchased a Nikkor 24/2.8 Ai-S to try out on the D40. I don’t know if metering is such a big deal in the long run, but it’s the one thing that’s keeping me eyeing the D200.
Here’s hoping!
Update 2008-02-25: apparently the hack is both hardware and electronic (source, the daily updates on Ken Rockwell’s site, no permalink). I guess that makes it slightly more complicated than just a firmware hack, that I had naively hoped for.