By default WordPress category archives are sorted by date.  This is fine when you’re publishing a blog but if you’re using WP for other reasons you might want to adjust the way the archives are sorted.  This is done rather easily by creating a new filter in your functions.php file like this:

//filter to alphabetically sort category archives
add_filter('posts_orderby','sort_category_archive_alphabetically');

And then creating a new sort function like this:

function sort_category_archive_alphabetically($orderby )
{
 if (is_category())
 {
 return "post_title ASC";
 }
 return $orderby;
}

In this example I’m alphabetically sorting all categories.  You could restrict it to a specific category by changing the is_category() call to include a category ID (is_category(8)) or by including a category name (is_category(‘Your Category Name’)).

I’m doing a simple sort by post_title here but more complex sorts are possible.  For example, the WordPress API gives a more complex example that explains how to do a LEFT JOIN in the SQL to select posts and sort by values in tables other than the WP_POSTS table.