D'Arcy Norman

I needed a way to display login form on the front page of a WPMU network if a person wasn’t already logged in, and a bit of info about the user, a list of their sites, a link to create a new one, and a link to logout. I could have done it by hacking the theme’s templates, but that locks you into a specific theme. With the shortcode, any theme can display this, on any page (or post, but why would you do that? whatever. it’s your site…)

User Info Login Shortcode

This plugin provides a [user_info_login] shortcode to let you embed a User Info or Login section without farting around with page templates or widgets

Emanuela Castorina

This plugin in a multisite installation shows the ID of the current site/blog in the admin bar menu. The ID of the current site/blog is linked to the site info page. 
It adds also a custom column with site id information inside the sites list table. 
It can be installed only on a multisite.

Wp Show Site ID

This plugin in a multisite installation shows the ID of the current site/blog.

User Info Login Shortcode vs Wp Show Site ID