A context-sensitive popup category list for Textpattern, shows only categories associated with the current section.
<txp:zem_popup_cat /> creates a popup/dropdown list similar to
<txp:popup type="c" />. It shows categories in a context sensitive manner. On the front page, only categories which contain active articles will be included in the list. On a section page, only categories which contain active articles from the current section will be included.