Wishy, I have a D50 - a very affordable easy to use camera. The new D40 is somewhat smaller (like a Canon 350 / 400) and I felt it was a bit tiddly in my hands (as the actress said etc).
The 18-55 standard lens with the D50 is fine for general stuff. However, to get decent shots of cars on the track you need to go longer. Having reviewed the photos I had previously taken at Sebring (and Le Mans) on my old Fuji S5000, I calculated that I was generally shooting at an equivalent focal length greater than 200mm.
Bearing in mind the 1.5 x field of view factor on a DSLR CCD, my dilemma was -
1. Spend a sh*t load of money on a 'fast' 70-200 f2.8 lens - more than £1000! or
2. Try the cheap 55-200 and maybe look for something else over 200mm.
Well, option 2 suited me (surprised!) and having read about the new 70-300 f4.5 VR lens, I went and tried one of those - and bought that.
So, my current 'general purpose' lens is the 18-70 and I will use the 70-300 VR for track shots.
Whilst I would like faster f-stop lenses (who wouldn't) I can't justify the cost and don't fancy the extra weight.
All the above lenses are Nikon by the way.
I'm sure that, between all of us Nikon users, you can get a feel for the variety of lenses available.