Example interfaces I can think of:
Priority Tags like Priority Inboxes
Sub-tree labels (mostly used by Google apps, sub-tags that have limited levels acting like two level folders)
Outliner indentions
Saved Searches/Custom Filtered Saved Searches
Excel like columns
Predefined Icons like Starred Bookmarks
Automatic Recommendation Tags
Collapsible Primary Map Categories in Mindmaps
Wiki-like tagging
Software tagging as seen in software sticky notes
Pending Tags (can't think of any but I've recently played Evil Genius where you right click to tag a spy for kidnapping, ignore or bully)
