If you budget can afford it, go for the Canon 20D.
Otherwise pick the Rebel XT or the Nikon D70S.

The size of memory card determines how many photos you can get on a card.

The Canon 20D specifications is for a 256MB card:
So I have multipled all figures by 4 to get the following:

8 megapixel fine quality .jpg = 264 possible shots.
RAW = 108 possible shots.

It is also possible to get both .jpg and RAW on each shot. If you do that, the capacity is approx 72 shots for a 1GB card.

For Nikon at 6 megapixels there would be about 25% more possible shots.

Canon recommends that you buy a fast card if you want to take a large number of rapid fire shots.
The SanDisk Ultra II is a good choice.

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