The nodeorder module gives users an easy way to order nodes within their taxonomy terms.
By default, the taxonomy module orders listings of nodes by stickiness and then by node creation date -- most recently posted nodes come first.
The nodeorder module gives the user the ability to manually put nodes in any order they wish within each category that the node lives.
There are two ways that a user can order nodes within a category. The first is to use the "move up" and "move down" links that can be configured to appear on each node (especially useful when looking at lists of taxonomy terms). The second is to use drag and drop, which appears on the administrative listings of nodes in a category.
For a comparison of nodeorder with other node ordering modules have a look at this handbook page: http://drupal.org/node/398508.