Without further delay, have a look here!

Straight from the site:

Lightbox is a simple, unobtrusive script used to overlay images on the current page. It’s a snap to setup and works on all modern browsers.

That’s all there is to it.  Simple set up.  A few instructions and you’re on your way to having some nice smooth lightbox image effects on your page.

Over at Dynamic Drive they have such a pop up. It’s called an interstitial content box. Fancy name eh? It’s easy to implement and easy to customize. I do find the settings for how often it pops up to be a little off. This might be due to where I’m having it pop up though.

Click here to pop into a new kind of pop up!

Description:

This is a Interstitial Box script that uses Ajax to fetch and display the contents of external pages on your server as an interstitial. As the content is being shown front and center on the page, a partially opaque “veil” appears behind it that covers the actual webpage, ensuring all eyes is on the interstitial. A robust frequency control system lets you control how often the interstitial box should appear so it doesn’t become intrusive. Whether you’re displaying an ad or an announcement, you can be sure people will notice it thanks to the Interstitial Box!