the 450D is a great DSLR for a beginner. it's in the same vein as the 350D but with a few more features and a higher megapixel count (12.2 as opposed to 8.0).
there is also the new
1000D which is a step down from the 450D and is of course also cheaper.
my main problem with the 1000D however is that it lacks spot metering (for an explanation
click here) which i personally think is very important for even a hobbyist photographer, especially when learning techniques and developing a photography style. for that reason alone i would go with the 450D over the 1000D if you're thinking of making this into a serious hobby.
i have the 450D and i can vouch that it's a wonderful camera. all the features are real easy to get a hang of even if you don't know everything about photography. even an idiot can take beautiful pictures on this camera, in automatic mode.
speaking of which, if you don't have a willingness to learn and experiment (although i assume you do!), don't bother with a DSLR. i know a couple of people who have DSLRs and shoot all the time on automatic mode. i think, however, it's a complete waste of a beautiful camera not to learn how to use it properly. educate yourself on the basics of exposure, how light works, and how your camera itself operates and you'll really discover the joy of photography through a DSLR.
if you want to see some examples of photos taken with the 450D (with the kit lens, because that's all i have, hehe) then you can check out my flickr:
http://flickr.com/photos/laurench/ (pages 1-3 and the first row of 4 are all taken with the 450D)
of course, if you want to save money, you can get a 400D. a lot of people tell beginners that the improvements on the 450D are not worth the current higher price tag, and that the 400D is good enough for novices. take a look at the changes the 450D made over the 400D and then decide for yourself:
http://www.dpreview.com/news/0801/08012415canoneos450dchanges.aspa nikon expert should come in here and talk a little bit about nikon... i honestly don't know much about their cameras or what they offer. i would advise you though to stick with canon if you want to have the possibility of sharing and swapping lenses with your dad.
hope this helps and if you have any questions about the 450d specifically you can ask.
