Here is mod for mantis.

	User Details.

It keeps additional user data like first name, second name, patronymics (for now) but can handle more.
It was designed for 0.17.5 mantis version, so that API is quite old.

Installation.
user_details.php - shows info on users.
manage_user_details.php - self-explanatory
user_details.sql - mysql dump for updating schema
user_details.diff - a thing that should be applied to scripts (adding menu links and handling data)

Hope, u'll enjoy it.