ZeroT

Shows a SplashScreen to visitors who enter the websites in their Browser or come from another site by referer. The SplashScreen appears only at the frontpage.

SimpleSplash

Shows a SplashScreen to visitors who enter the websites in their Browser or come from another site by referer. The SplashScreen appears only at the fr …

Vast HTML

A great plugin for any great WordPress powered site. 
Its very often that you update your site, or decide to try new themes and make sure everything is 
ok before you want your visitors to view the site. Sometimes you want to stop them before the view your 
site while you are completing updates or even just getting the site started. This plugin will 
keep away the users you don?t want and do it with a great look that will get the visitors attention. 
This is a WordPress plugin on the file available on Theme Forest. You will need to purchase this plugin for it to work correcly. 
Plugin also has a updater to let you know when a new version is available.
Withoutreligion.com has very kindly offered to set up a full time demo of the site. 
http://withoutreligion.com/vinta_demo/

Vinta Construction

adds a splash screen to your site for construction or maintenance reasons. Has a configurable countdown.

SimpleSplash vs Vinta Construction