jroakes

This plugin will give you the ability to pull up any (non-Super Admin) user and in one click add that user(with a global role) to all sites in your MU install. Likewise, if you want to remove a user from all sites it is one click as well. CAUTION: WordPress has an optional mechanism when deleting a user from a site that will allow you to assign that users posts to another user. I have ignored this for this release. Please take a DB backups until you are used to this plugin and Multi-Site.

Multi-Site User Replicator 3000

WP3.1 multisite "mu-plugin" that allows you to add a user to all sites or no sites. Just drop in mu-plugins.

Otto Kekäläinen

Viljami Kuosmanen

Onni Hakala

Currently WordPress doesn’t allow you to add custom bulk actions. See codex. Adding them is super easy with this plugin.
This is based on solution found here: http://www.skyverge.com/blog/add-custom-bulk-action/ 
This plugin just makes it more easier to use.
Plugin adds a class named Seravo_Custom_Bulk_Action which you can use to easily define custom bulk actions. 
See documentation and examples here: https://github.com/Seravo/wp-custom-bulk-actions/

Custom Bulk Actions

Currently Wordpress doesn't allow you to add custom bulk actions. Adding them is super easy with this plugin.

Multi-Site User Replicator 3000 vs Custom Bulk Actions