A common request that comes up in the forums is to be able to use distinct templates for each category archive. The obvious solution is to use the MTSuplemental Category Tags to include category specific code.
However, this solution really only works for templates that are fairly similar and only differ in a few places, such as which style sheet they use, etc. Using conditional tags also makes it difficult to edit templates in an editor such as DreamWeaver.
Still, you can implement proper per-category templates by using template modules. For each category make a corresponding template module. The actual category template then simply includes the appropriate module based on the active category.
If you use my MTIncludePlus plugin and name your category template modules in a consistent way, your main category template becomes as simple as this:
<MTIncludeModule>Category: <MTCategoryLabel></MTIncludeModule>
Here are more details on how to do it.