KaeruCT

This plugin allows passwords for password-protected pages/posts to be passed directly through the URL.
The query string parameter that should contain the password is <code>pw</code>.
For example, if the URL of your post is <code>http://myblog.com/password-protected-page/</code> and the password is <code>PASSWORD</code>, 
then just append <code>?pw=PASSWORD</code> to it.
If the URL already contains a query string (for example, <code>http://myblog.com/?p=5</code>), then be sure to append <code>&pw=PASSWORD</code> instead.

Password Passthrough

This plugin allows passwords for password-protected pages/posts to be passed directly through the URL.

Marcello Scacchetti

Display on password protected pages/posts a custom specified text instead of the WordPress default one.
A few notes about the plugin: 
* Actually doesn’t support i18n, should be supported in the next release 
* Actually doesn’t support message multilingual message translation

Custom Password Protected Text

Custom text message for password protected pages and posts

Password Passthrough vs Custom Password Protected Text