Ruven

This plugin registers a custom post type for galleries and a taxonomy for categories.
Selected themes by Ruven provide templates to display galleries. 
In other themes you most likely have to add them by yourself.

Ruven Themes: Gallery

RT Gallery enables a "Gallery" post type and "Category" taxonomy.

Mike Selander

This plugin appears to no longer be needed, but I am cleaning it up and maintaining it for those on legacy versions of Envira Gallery.
Envira Gallery is an amazing gallery plugin, however it displays its metabox on every post type on your site. This is unnecessary and distracting for you and your clients. This plugin gives you an easy to use settings page that allows you to quickly change the post types that the metabox shows on.
The plugin will default to restricting the metabox from all post types once installed. I am not affiliated with Envira Gallery, just helping people manage their backend.
Note: you must have the Envira Gallery Lite or full plugin installed for this plugin to do anything.

Envira Tamer

Control which post types Envira Gallery meta box field shows up on

Ruven Themes: Gallery vs Envira Tamer