Jan Štětina

Includes custom HTML/CSS/JS code in the section on every blog in the network.
Very simple, but sometimes useful plugin.
After activation visit Network Admin –> Settings –> Multisite wp_head Code for setup. Nothing else is needed.
Developed for private use, but has perspective for more extensive usage. I can’t guarantee any support in the future nor further development, but it is to be expected. Kindly inform me about bugs, if you find any, or propose new features: <a href="mailto:zaantar@zaantar.eu?subject=[multisite-wphead-code]" rel="nofollow ugc">zaantar@zaantar.eu</a>.

Multisite wp_head Code

Includes custom HTML/CSS/JS code in the  section on every blog in the network.

WP Scripts Customizer provides you with two fields that will output to the head section of your site before the closing head tag and just before the closing body tag. These will appear on every page of the site and are a great way to add analytic code, Google Font and other scripts. Only user with unfiltered_html capability that able to access these fields. unfiltered_html allows you to post HTML markup or even JavaScript code. Developed by <a href="http://themehall.com" title="themehall" rel="nofollow ugc">themehall</a>

WP Scripts Customizer

WP Scripts Customizer allows to enter scripts you would like output to head and footer of your WordPress theme page via WordPress Theme customizer.

Multisite wp_head Code vs WP Scripts Customizer