hauxh

This plugin allows you to require a secret key that is passed via the URL: http://example.com/post-title/?key=[string] 
Specify the key in a custom value called “key” with the [string] or use the built in widget.
Stable version of the plugin are pushed to the WordPress repository, 
but the latest version of the plugin can be found at: 
https://bitbucket.org/excion/wpkeyme/
Issues/Bugs: https://bitbucket.org/excion/wpkeyme/issues

WPKeyMe

This plugin allows you to require a secret key that is passed via the URL: http://example.com/post-title/?key=[string]

mrdl

Adds the current logged in user ID to a specified string
<pre><code>[user_link url="https://domain.com/link"]A link[/user_link]
</code></pre>
Will output the following HTML
<pre><code><a href="https://domain.com/link?user_id=1">A link<a/>
</code></pre>

Append User ID

A plugin which adds some shortcode to append the current user ID to a link (href).

WPKeyMe vs Append User ID