Mark Jaquith

<ol>
<li>Check a category.</li>
<li>Uncheck “Uncategorized”.</li>
<li>Mutter “stupid ‘Uncategorized'” under your breath.</li>
</ol>
Sound familiar? With this stupidly simple plugin, you just have to do the first step. When you check a category and the default category was the only thing checked before you clicked, it’ll uncheck the default category for you. Boom.

Categorized

Unchecks the default post category when you first select a non-default category

josecoelho

This plugins add meta data to the wordpress categories and terms. 
It Creates a wp-termsmeta table to store the entered meta. 
It adds input fields to the category and other term administration interface to enter the meta values. 
It provides functions to retrive / create / update / delete the category and terms meta. 
It can be used to add meta to custom taxonomies (terms).
This plugin has been tested with WP2.8.6 and WPmu2.8.6 and WP3.3.1
<h3>Update Log</h3>
1.2.8 : Add Brazilian Portuguesetranslation thanks to josecoelho
1.2.7 : Small fix to make the image fields work in WordPress 3.4.
1.2.6 : Fix bug introduced in 1.2.5, allowing images to be inserted into posts again.
1.2.5 : Small fix to make the image fields work in WordPress 3.3.1.
1.2.4 : Small fix to make the meta list appear in the taxonomy edit page with WP3.0.1. && WP3.0.4 (thanks to webgrafia).
1.2.3 : Add a new meta type “check-box” with meta_value of “checked” when the box is checked (thanks to Joseph).
1.2.2 : Small fix to make the meta list appear in the taxonomy edit page with WP3.0.1. && WP3.0.4 (thanks to Patrick).
1.2.1 : Small fix to avoid problem wih global variables in the taxonomy list with WP3.0.1. (thanks to Jeff).
1.2.0 : Major release. Add the terms meta administration form on all terms (category / Tags / custom taxonomies) for WP version 3.0 and above.
1.1.1 : Fix a typo error when no meta has been configured.
1.1.0 : Major release. Test and debug to be fully compatible with version 3.0.x . Add the new “image” type for meta.
1.0.3 : Fix an error on the meta update method thanks to Tom Ransom for sending the fix.
1.0.2 : Debug when no meta is set.
1.0.1 : Add the possibility to replace special chars into meta name in the meta creation form in the option page.
1.0.0 : Add the option page to easily configure the meta list
0.0.1 : plugin initial creation.

Category Meta plugin

Add the ability to attach meta data to the wordpress categories and terms.
It can be used to add meta to custom taxonomies (terms).

Categorized vs Category Meta plugin