Add Multiple Users for WordPress is a WordPress plugin by happynuclear that provides a simple interface for an administrator to bulk register up to 50 WordPress user accounts in a single form.
Each new user can have a custom username, a customised or randomly generated password, an email address, first name, last name and website data added automatically.
A single page plugin with a simple, functional input form to register up to 50 users at a time
On-screen validation checks for the uniqueness of usernames and email addresses as you type, as well as optional email address validation
Includes options to enable or disable notifying new users of their login information
The ability to set all new users to a single Role or set each user individually
Optional password field for each user, with a WordPress-generated password if you leave it blank
The optional ability to generate dummy email addresses for users without email access
Plugin homepage: http://www.happynuclear.com/sandbox/amu/add-multiple-users-for-wordpress.php