WP Lightbox 2 is awesome tool for adding responsive lightbox effect for images and also create lightbox for photo album/gallery on your WordPress blog
Display a popup to your WordPress site: age restriction popup for adult-content site ★ multilanguage popup with qTransalte-X ★ very easy to use
Sticky Popup is a simple and easy wordpress plugin used to add popup on fixed position like bottom, left or right side with CSS3 effects.
Easily create a popup for your WordPress site.
Clean announcement plugin that reveals a neat popup when users visit your site. You can set who sees the announcement and when to display it.