Block Reserved Usernames
Prevents anyone from registering or being created with usernames like admin, support or root that look official or invite attacks.
Snippet Library
Users snippets for WordPress
Snippets for user accounts, roles and profiles: extra profile fields, new columns in the users list, last-login tracking and tighter control of what each role can do. Handy for membership sites, client sites and teams with many authors.
Require an Invite Code to Register
Adds an "Invite code" field to the registration form and only lets people sign up with one of your codes, each with an optional limit on how many times it can be used.
Sign-Up Prompt Near the End of Posts
Invites logged-out readers to create a free account three quarters of the way through each article, when they are most engaged.