avdude

This wordpress plugin allows you to create and download a backup of a plugin or your entire plugins directory. 
Very useful to use just before updating a plugin. 
Adds menu item to Plugins & Tools

Plugin Grabber

This wordpress plugin allows you to create and download a backup of a plugin or your entire plugins directory.

If you are a developer and want your customers to install plugins from your site without downloading and uploading them manually – just install our plugin and provide the URL. If you are a website administrator and you buy third-party plugins from developers – you can use our plugin for quick and easy installation. Just ask the developer for a link and past it into URL field.
Install Plugin From URL 
You can easily let your customers install all your plugins right from their website administrator area. When a user goes into his/her backend and click on the “Install from Web” tab, your extension can be found and the “Install” button appears, so the user can just click to install your extension.
Main Features
<ul>
<li>Install from any URL</li>
<li>No coding required</li>
<li>One-click installation</li>
<li>Create your own repository for your customers</li>
<li>No need to download and upload archive</li>
<li>Adding new feature to WordPress dashboard menu</li>
</ul>

WP Install From Web

WP Install Plugin From Web allows you to install any plugin from a URL. All you need to do is to insert a specific URL and click the Install button.

Plugin Grabber vs WP Install From Web