if you go with a canon select the 10d, 20d, 30d range as they were semi pro / high amateur cameras to start with rather than budget dslrs (300d, 400d, 450d)
they have more features and better build quality as they have magnesium bodies rather than plastic.
i have had a 10d for the past 4 years and still use it and get great results, i would recommend a 30d if you can get one for the price, if not a 20d is still a good option.
also remember its not all about megapixel etc, you camera will only ever be as good as the glass you put infront of it soa 20d which is a little cheaper with money for decent lens isnt a bad option