Posts sorted by categories?

So, I’m interested in creating a page that lists posts by category.
Like this:

PHOTOS:
29/May/2004 @ 2:52 am Edit This
the_content
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28/May/2004 @ 6:27 am Edit This
the_content
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@ 1:10 am Edit This
the_content
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REVIEWS:
29/May/2004 @ 5:02 am Edit This
the_content
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@ 1:34 am Edit This
the_content
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28/May/2004 @ 9:46 am Edit This
the_content
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Any advice as to my best approach? What the easiest way to test if a post is in a category? (I know that in_category() tests the current $post.) Has somebody done something like this already? (It seems like something there would be a demand for.)