In tDiary with BlogKit?, you can specify the category of the article in the title, in the form of:
[category] the title of the article
In the generated HTML, '[category]' is a link to the view of the category. You can specify as many categories as you want.
If you want to show the information of categories in the sidebar, add the followings to
<div class="sidemenu">Category:</div> <%=blog_category_form%> <%=blog_category_entry%>
shows a dropdown list to select a category to be shown.
shows the list of titles which can't be shown in the category view.
You can get all of categories and titles with 'blog_category_cache_restore' method, and use this information in your own plugins.