As I regularly forget to update this page, you can find an updated list on NuGet and the Umbraco Marketplace.
UmbNav
A flexible, draggable link picker for constructing site navigation menus, big or small, in Umbraco 8 and Umbraco 9+.
You can find this plugin at the following locations:
Nuget
Our Umbraco
GitHub (source code)
MegaNavV8 - Retired
A flexible, draggable link picker for constructing site navigation menus, big or small, in Umbraco 8.
You can find this plugin at the following locations:
Nuget
Our Umbraco
GitHub (source code)
Our.Umbraco.MaskBackoffice
This package will allow you to easily mask the umbraco backoffice behind a subdomain.
You can find this plugin at the following locations:
Nuget
Our Umbraco
GitHub (source code)
ApplicationInsights.StatusCodeFilter
Status code filter for Application Insights to record as success instead of failure for Umbraco 8.
Nuget
Our Umbraco
GitHub (source code)
Umbraco.TimePicker
This package adds a time picker to the Umbraco V8 backoffice.
Nuget
Our Umbraco
GitHub (source code)
UmbracoForms.uCaptcha
A simple to use and integrate captcha plugin for Umbraco Forms which supports both hCaptcha and reCaptcha.
Nuget
Our Umbraco
GitHub (source code)
Maintenance Manager
Quickly turn your site on or off for your visitors, via a nice and easy dashboard.
Our Umbraco
GitHub (source code)
ActiveIS.UmbracoForms.CustomEmail
A customizable email template which does not include the form data.
Nuget
Our Umbraco
GitHub (source code)
ActiveIS.UmbracoForms.Loqate
This package adds Loqate address verification to Umbraco Forms.
Nuget
Our Umbraco
GitHub (source code)
ActiveIS.UmbracoForms.Intl-Tel-Input
Intl-Tel-Input for Umbraco Forms.
ActiveIS.UmbracoForms.ConfirmInput
Make sure the value in two text inputs match with Umbraco Forms.