BuddyPress.org

You need something like this:

<div id="tab2_login" class="tab_content_login">
<div width = "300px"><h3 class="topline">Register for this site!</h3>
</div>
<!--<div id="tab1_login" class="tab_content_login" style="margin-left: 560px;width: 130px;margin-top: -20px;">Back to login</div>-->
<p>Sign up now for the good stuff.</p>
<form method="post" action="<?php echo site_url('wp-login.php?action=register', 'login_post') ?>" class="wp-user-form">
<div class="username">
<label for="user_login">Username: </label>
<input type="text" name="user_login" value="" size="20" id="user_login" tabindex="101" />
</div>

<div class="email">
<label for="user_email">Your Email: </label>
<input type="text" name="user_email" value="" size="25" id="user_email" tabindex="102" />
</div>

	<div class="login_fields">

	<?php do_action('register_form'); ?>
<p class="login-submit">
<input type="submit" name="user-submit" id="wp-submit" value="Sign up" class="user-submit" tabindex="103" />
</p>
<input type="hidden" name="redirect_to" value="<?php echo $_SERVER['REQUEST_URI']; ?>?register=true" />
<input type="hidden" name="user-cookie" value="1" />
		</div>
	</form>
</div>