Those cool popup windows

Lately I’ve seen many sites use popup windows that aren’t a browser window, but rather, a popup that is done via CSS, ajax or something. I’ve done some searching on google and can’t find a good basic tutorial. Can anyone help recommend one? I want to change my site from using a standard browser window popup, to these cool new ones where the rest of the webpage dims while the popup takes the focus.

Thank you!

you’re probably thinking of lightbox

They’re “lightboxes”.

List: http://planetozh.com/projects/lightbox-clones/

Ones I like:
http://colorpowered.com/colorbox/

The original lightbox is probably a bit outdated now.