Zim - A Desktop Wiki
Zim supports the use of tags to organize pages. Tags are keywords or labels that are used to categorize pages.
Tags can be used anywhere in a page using the "@" prefix. Like this: @example @tags
To find context based on tags you can use the Search dialog. For example to find all pages tagged with "@example" you can search for "Tag: example" or just for "@example". Since tags are cached in the index, this search is much quicker than a full text search for random words.
There is also a plugin that will add a tag cloud and a page index organized by tag in the side page, see also Plugins:Tags