Stefano Garuti

As you know WordPress’s Registration Form is only displayed in it’s own page, and if you want to invite a user to register, the only option you have is to provide a link to the registration page. 
With this plugin you have a new widget that insert a Registration form in your sidebar. 
The new registration form supports all the hooks that the standard Registration page does, so you can use it safely even with other plugins like Registration Plus that add fields to the form.
UPDATE and NEWS at: http://www.wpmania.it/registration-widget/

Registration Widget

This plugin provides you with a new Widget that inserts the Registration Form in your sidebar (or wherever a widget-area is defined in your theme).

Miaz Akemapa

Regnomail is a plugin to customize your registration form. It disable sending email confirmation during user registration to admin and to user itself.
Regnomail Features:
<ul>
<li>Disable email confirmation to user during registration</li>
<li>Disable new user email notification to admin</li>
<li>Disable user change password notification (lost password) to admin</li>
<li>Show password input form, so user can input their own password</li>
<li>Show First and Last name input form</li>
<li>Change login / registration logo image.</li>
</ul>
Read more details here: 
<a href="http://www.vnetware.com/regnomail" rel="nofollow ugc">http://www.vnetware.com/regnomail</a>

Regnomail

Disable new user registration confirmation email.

Registration Widget vs Regnomail