This is sort of a hack but if you want to make categories appear in your modules, then you can do the following. Thank you to sylvie

• Place mod-categories.php into /modules/mod-categories.php
• Place mod-categories.tpl into /templates/modules/mod_categories.tpl

A new module has been written in 1.10 - you can find it in tikiwiki Head CVS. The parameters are

type=wiki page|article|faq|blog|image gallery|image|file gallery|tracker|trackerItem|quiz|poll|survey|sheet|...
deep=on|off
categId=0|..
style=tree|vert|horiz|plain|phptree

You can filter on the type of objects, you can begin a tree from a subcategory, you can decide the module aspect (see the phplayers documentation for the details)
This module works if you use other phplayers menus. And you can use several times this module.
Note: you can't use directly this version in 1.9 as the multiple use of phplayers menu needed some global changes but you can find an earlier working version (if you use only one phplayer menu) in sourceforge modules/mod-categories.php
sourcefoge templates/modules/mod-categories.tpl

sylvie