Nikon D40 for me, as for most owners, is a first
DSLR. As you gain manual control over your camera and with opportunities to change lenses and control
the light off the camera, a whole new horizon opens up, but it comes at a co$t, as you realize your purchases have only began.
D40 comes with a great kit lens. My advice to anyone who's buying that camera, or any other first DSLR, is to wait and see what you like shooting the best. If it's nature, you'll want a zoom lens, and
55-200 VR is a great value for the money. If you like shooting
people, you might want to invest into
50mm f/1.8, which can be a pain to focus in a low light, but offers great
shallow depth of field.
But one accessory I would recommend buying right away is an external flash that can bounce the light off the ceiling. Instead of having people
washed out with light on your pictures to make people look dead, you can let the flash spread evenly across the room, as you see it on the phone on the right, thus creating a natural look to your photos instead of usual flash look.
If you own Nikon and you're looking into buying a flash, I recommend skipping SB-400, and going straight to SB-600. The value and options you get worth extra $70 you'll pay for it, and eventually as your skills improve, you can implement SB-600 into your lighting setup in a way you wouldn't be able to with SB-400. I owned SB-400 this whole time, but have regrets about my purchase feeling a lack of features SB-600 or SB-800 would have offered me, so I just bought another flash. You're welcome to ask any questions about this, as I get a lot of emails about SB-400.