After buying myself a D80 I was so excited that I needed to share the experience. So I bought a D40 (the 2-lens kit), and had it sent to a long-term internet friend. She was blown away but terribly intimidated. She called me when it arrived but I couldn't even get her to put a lens on the first night. She was used to point and shoot cameras and was almost afraid to touch her D40. I called her the second night and finally convinced her to pop a lens on the camera, put it in Auto mode, and snap off a shot.
That was all it took. She went around her house taking pictures of everything and hasn't put the camera down since. It goes everywhere with her and she loves it! She lives in a gorgeous area and quickly made me jealous with the beautiful pictures she has been taking. Once you have a D40, it's just not going to get any better. The pictures your new camera can produce are as good as any coming from any D-SLR at any price.
She loved it so much I recommended one to my mother and she also bought the two lens kit (18-55mm and 55-200mm).
There is one drawback to D-SLRs and it's such a fact of life that from what I've seen, it has slipped everyone's mind here. The problem is dust but you needn't be intimidated by it. It will get into your camera and make itself very comfortable on your IR filter (right on top of your sensor). You'll eventually see some dark little blotches on some of your photos.
So I would recommend being ready for the inevitable. Get yourself a blower with a filtered intake port. Giotto makes several you can get for around $10. That's your first line of defense against dust. I would also recommend looking into a brush system like those made by "Invisible Dust". They'll run you a bit more money (around $80), but will serve as your second line of defense against dust.
If you end up with some spots that just won't go away, you can get them by using special cleaners and sterile swabs (1-use each), specifically made for cleaning your IR filter (also known as a "low-pass filter"). There are several videos on YouTube demonstrating the proper techniques. Be very careful but again, don't let the process intimidate you. You can pay someone else to clean your filter (often referred to as "cleaning the sensor"), but unless you're just terribly intimidated by the idea, it's far more cost effective to learn exactly what you're doing, get the proper supplies, and just clean it yourself. The swab and cleaner kits can be had for around $20. Just make sure to get a cleaner recommended for ITO (Indium Tin-Oxide), coated filters because the D40 does have this anti-dust coating. Several companies such as "Photographic Solutions" (photosol.com) produce these kits.
The more you change lenses the more dust is likely to get into the camera but some will likely get in even if you never change lenses. Some people just clean their IR filter on a standard schedule but I don't think it's really necessary unless you start to detect those dastardly little blotches in your photos.
I'm sharing your excitement at the moment. My D80 has been my passion since I got it and yesterday I received my new Nikon D200. Now I can have two lenses mounted, one on each camera, and switch back and forth without a lens swap. I love to shoot macro (not that I'm any good at it but I try), and often find some of the best telephoto shots go by while I have one of my macro lenses on the camera.
Lots and lots to learn but it's amazing fun and I'm sure you'll become so absorbed in your new D40 that bills, cars, cleaning, groceries and the rest will all fade into the background.
If you're looking to build a collection of useful accessories, I completely agree with those suggesting a camera bag, case or pack. I ended up buying an SLR holster, a 2-SLR bag and two different Lowepro packs. Some things I felt my friend might need include the Giotto Rocket Blaster, a wireless Nikon remote control (about $15), a spare battery and a 70-300 macro lens. She hasn't had to use the Rocket Blaster yet and won't need the remote until thunderstorm season hits in her area but the battery and Sigma lens are getting a good workout.