lightweight cross browser jQuery popup plugin. It's not creating your popup but doing all the logic as opening, closing, centering on resize & scroll, creating a modal overlay etc. It can open any container you create with all kinds of content.
Preview web pages inline in Google Reader, collapse the header and sidebar for more reading area, add favicons to feed subscriptions and more with Better GReader.
This module provides you both an API as an User Interface to create draggable inline windows which can be used to display messages, images, load drupal forms and lots of other things.