Sergey Biryukov

Allows to create users with usernames containing Cyrillic characters.

Allow Cyrillic Usernames

Allows users to register with Cyrillic usernames.

This plugin is available for reference only. Its functionality has been replaced and extended by <a href="https://wordpress.org/extend/plugins/cyr2lat/" rel="ugc">Cyr-To-Lat</a>.
The original author of this plugin is Anton Skorobogatov, who passed away prematurely in 2007. I decided to make it available for installation through the Plugin Browser/Installer. I take no credit for the creation of this plugin.
Converts Cyrillic characters in post slugs to Latin characters. Very useful for Russian-speaking users of WordPress. 
You can use this plugin for creating human-readable links.
Thanks to Alexander Shilyaev for the idea.

Rus-To-Lat

Converts Cyrillic characters in post slugs to Latin characters.

Allow Cyrillic Usernames vs Rus-To-Lat