Geweb

Use this plugin if you want allow users create their own sites based on your.
<h3>Arbitrary section</h3>
You can create your own HTML code of the form. 
Create file in your theme, put code from plugins/wp-auto-mu/geweb-mu/register.php to your new file and add_filter geweb-mu-register-path to rewrite file paht for the form.

WPMU User own site

Plugin allows to create site on user registration in WPMU environment.

Enej Bajgorić

Ever wanted your users to see all their sites in a list format, Well now you can using this shortcode!
Here’s how it works:
Install this plugin and then add [my-sites] onto a page or post where you want people to see all of their sites.

My Sites Shortcode

Ever wanted your users to see all their sites in a list format, Well now you can using this shortcode!

WPMU User own site vs My Sites Shortcode