We recently had a project in which the client’s design required a splash page. While we felt like we were traveling back in time to the year 2000, we went ahead and put it into a plugin. Feel free to use it—but please, use sparingly.
Cheers. 
Usage:
Step 1: Tell Splash where your splash page is located.
{exp:splash location="template_group/template"}
Step 2: On your splash page, set parameters for Splash.
{exp:splash show_again_after="3600" redirect_in="5"}
show_again_after: How long (in seconds) till the splash page is displayed again to the user. 3600 = an hour. This value is stored in a cookie.
redirect_in: How long (in seconds) till the splash page redirects.
redirect_to: This is an optional field if you wish to have the splash page redirected to a page other than the site’s index page.
