Over at NathanRice.net Nathan covers different methods you can use to accomplish utilizing alternate customized single.php templates for WordPress post categories, including a plugin he developed. There’s no native way to present different categories of posts in a special way (only pages), except perhaps hacking the posts query, or doing show/hide with CSS or jQuery. This page offers some easy to implement solutions.
Filtering WordPress categories using hooks
Ryan Marganti over at SoulSizzle.com runs through what WordPress hooks are, and how you might use them including some simple examples. He reviews WordPress filters, edits to your functions.php file, the get_terms hook, and where you might find out more references about hooks. This is a nice introduction for WordPress theme or plugin developer newbie. Check out his other posts while you’re over there.