The Nikon D40 has a very complete Record ("Shooting") menu for an entry-level camera. Most of the features of the D80 are repeated here, the primary omission being the ability to apply color filters to the image while shooting in black-and-white mode.

We particularly like the "tweak" adjustments for overall hue, as well as for each of the white balance presets. This allows very fine-grained tuning of the camera's color and white balance to match shooting conditions.

Here's another difference between the D40 and D80: The D40 only gives you full-EV steps for ISO adjustment, the D80 had 1/3 EV increments.

The D40's noise reduction option governs both high-ISO and long-exposure processing, there aren't separate controls for each.