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.

neojp

ZÆN

SplashGate is a splash page plugin. It does optional full page redirection that won’t mess up search engine indices, and makes permanently available a url that will always redirect to the actively splashed page. Alternatively, splash page content can be made to appear as an overlay (using fancybox) instead of redirecting.
Splash management is centralized, so it’s easy to see if a splash page is active, which page is the active splash, and to easily disable or enable new pages. There is also a dashboard widget, recurrence timing options, and overlay sizing configuration.

SplashGate

Caching and SEO friendly way to allow any page to be used as a splash page or splash overlay.

Vinta Construction vs SplashGate