I've been using menu position module (http://drupal.org/project/menu_position) for some time and this is a really handy module I must say. It lets you set an active menu item based on different conditions. For example: you want products menu item to be set as active while you 're browsing nodes of content type "Products".
But I really missed one part of functionality for this module: I wanted to make a menu item active depending on a vocabulary which current taxonomy page belongs to. For example, you have a menu item "Articles" and you want this menu item to be set as active while you browse any category page which belongs to vocabulary "Article categories".
So I created a menu positon vocabulary module (now is live on drupal.org: http://drupal.org/project/menu_position_vocabulary) which itself is a plugin for menu position module. It provides user with "Vocabulary" tab available in menu position settings. In this tab you can select one or multiple vocabularies, this will activate menu position rule for taxonomy term pages which belong to selected vocabularies.
Pretty simple :) Hope you'll be enjoying this little addition and yes, now I have a permission to create full projects on drupal.org, so get prepared for more cool modules, I already some on the pipeline.