Håkan Wennerberg

This is a very simple, yet effective plugin that strips away non standard UTF-8 characters from your various RSS and Atom feeds. A typical symptom that you need this plugin is if WordPress is generating non-valid XML for your feeds.

HW Feed Cleaner

If you ever had trouble with WordPress generating non-valid RSS or Atom feeds, this is the plugin for you.

g30rg3x

Since the release of WordPress 2.2 the character set has been set by default to UTF-8 and the users 
that come from previously versions of WordPress, may have some problems with the old Latin1 character set 
and the new default UTF-8 character set. 
This plugin has been designed and developed with the idea to do this complex task in a easy 1-click way, 
so it will no require any type of advance knowledge about the topic to make use of this plugin.
Attention: This plugin is no longer being maintained by the author
<h3>NOTES</h3>
This plugin makes and a irreversible job to your database so consider seriously the task to make a complete backup of your 
WordPress based site before proceed with the task. 
This plugin has been designed to be only compatible with WordPress versions 2.2.x and 2.1.x so running 
the plugin on other minor or major versions may have unexpected behavior.

UTF-8 Database Converter

Easily Converts the WordPress database from any type of character set to UTF-8 character set.

HW Feed Cleaner vs UTF-8 Database Converter