You can set up the CreateUserWizard control to automatically send an email when a new user registers.
The Email can contain the new user's registered username and password.
<%@ Page Language="C#" %>
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
CreateUserWizard Email
File: Register.txt
Thank you for registering!
Here is your new username and password:
username: <% UserName %>
password: <% Password %>
When the email is sent, the user's registered username and password are substituted for these expressions.