Many Open Source projects provide their icons for use in other projects. In addition, the licenses of many icon sets allow for remixing and extension. This is hugely beneficial to end-users, as it allows designers to distribute add-on packs without having to worry about complex licensing terms.
I've been using the new Twenty-Ten theme for WordPress on my personal website; it's great out of the box, but I wanted to display my custom post types and taxonomies in the same format as it uses for categories and tags. The function is broken into two parts: ucc_get_terms() returns a multidimensional array of the post's taxonomy name(s) and each taxonomy's term links; ucc_get_terms_list() gets the taxonomy information and formats the array for display in the template.
The WordPress Categories Widget currently only handles the category taxonomy. I've modified it to allow the user to select a taxonomy, and tied in the Tag Cloud Widget code to give the user the choice of display formats: list, dropdown, and cloud. Multiple instances are possible, providing the user with an easy method for displaying links to user-built taxonomy terms.
preg_replace_callback() is used to fix the JavaScript for the dropdown menu; instead of generating the default ?query_var=value format, it uses get_term_link() to generate the term URL.
By default or design, the WordPress function get_calendar()[^1] does not handle post types other than post. I've updated it as the standalone function ucc_get_calendar() to allow it to accept a $post_types array; the included filter function ucc_get_calendar_filter() will allow for seamless integration via functions.php without requiring additional editing of Theme templates. (Note that the filter will also apply to the Calendar Widget's output.)
Again with the custom post type extensions. This function lets the native WordPress wp_get_archives() [^1] [^2] know about public custom post types; just add it to the functions.php of your theme. Of note: the builtin link post type can be included at the array_merge() point; I just had no use for it.