Flourish Pixel

Remove/Exclude specific categories from site RSS Feed. You just need to install this, then place your category id in it’s option page and save. That’s all. If you want to exclude more than one category, then place them one by one and separate them by comma.
For Example: -1,-2
**Note: you must need to use minus sign (-) before category id.

FP RSS Category Excluder

Remove/Exclude certain categories from site RSS Feed.

PoseLab

A simple plugin that displays a list of all categories except those selected in widget preferences. Unlike other similar plugins like “Almost All Categories Widget”, Categories but exclude uses the latest version of WordPress Widget API, which is multi-widget, which lets you use the wigdet more than once. Mostly, I created the plugin to use it with the plugin “WPML” along with “Widget Logic” to use the same widget for each language.
This will allow you to create a custom category list which will show the categories you want, and will hide the categories you do not want. For example, say you have a particular category you don’t want to be displayed named “Announcements”. You can use this plugin to display all of your other categories, except the category “Announcements”. You are not limited to just excluding one category; you can exclude multiple categories.
Languages:
<ul>
<li>Spanish (es_ES) – <a href="http://poselab.com/" rel="nofollow ugc">PoseLab</a></li>
<li>French (fr_FR) – <a href="http://www.tradpress.fr/" rel="nofollow ugc">TradPress</a></li>
</ul>
If you have created your own language pack, or have an update of an existing one, you can <a href="mailto:javierpose@gmail.com" rel="nofollow ugc">send me</a> your gettext PO and MO so that I can bundle it into the Categories but exclude. You can download the latest POT file <a href="https://plugins.trac.wordpress.org/browser/categories-but-exclude-widget/trunk/categories-but-exclude.pot" rel="nofollow ugc">from here</a>.

Categories but exclude

Displays all categories except those selected in widget preferences.

FP RSS Category Excluder vs Categories but exclude