The Canon EOS Digital Rebel XSi (450D) will be widely available in two weeks. The kit with the XSi camera body and the new EF-S 18-55 mm f/3.5-5.6 IS
lens will list for about $900.
Expect the availability of this new model to drive down prices on the older Rebel XTi (400D) even further. The kit with the Rebel XTi camera body and the older EF-S 18-55 mm f/3.5-5.6 non-IS
lens normally goes for about $600.
The older 18-55 lens without the image stabilization isn't as good as the new $170 lens, but it is quite versatile, covering an equivalent field of view of a 28.8-88 mm lens on a 35mm camera. This is a very useful range of focal lengths.
If you want to take photos indoors without a flash or if you want to take photos with a shallow depth of field (to isolate your subject in focus against a blurry out-of-focus background ("ooh, Bokeh!"), then you may want to add the $90 "nifty fifty" EF 50 mm f/1.8 lens. This is Canon's least expensive EF lens, but it can take some very nice photos. It's fast (it gathers 10.1 times as much light as the kit lens' maximum f/5.6 aperture at this focal length), sharp, and offers a wide aperture for a shallow depth of field.
To reach out further, you may want to add the new $270 EF-S 55-250 mm f/3.5-5.6 IS telephoto zoom lens that you mentioned. This inexpensive telephoto includes Canon's excellent optical image stabilization to compensate for camera shake. This will not help with fast-moving subjects, but for stationary subjects, it allows you to take hand-held photos at much slower shutter speeds than would otherwise be possible. A clear image at 1/15s without a tripod is impressive.
Those three lenses would cover a pretty wide range without breaking the bank. What you spend on lenses only goes up (and up) from there.
Here are reviews of the lenses mentioned above:EF-S 18-55mm f/3.5-5.6 II
from the XTi kitEF-S 18-55mm f/3.5-5.6 IS
from the XSi kitEF 50mm f/1.8 IIEF-S 55-250mm f/4-5.6 IS
The lens that I usually have mounted on my EOS 40D is the EF-S 17-55mm f/2.8 IS USM
, which covers the same focal length range as the inexpensive kit lenses, for five times the price.