I have just added a cool new feature to my site which is available from www.snap.com. You should notice all the little speech bubble icons next to all my links to external sites which if you hover over the icon will open up a nice little popdiv containing various content preview.
For example hovering over the following link will show a screenshot of my website www.strictly-software.com. For new sites that have not been previewed before it may take a little while for the div content to load however once a site has been loaded the cached version should be pretty fast.
The following link which goes to another blog but because its also available as an RSS feed it opens up with that option and you should see a scrollable list of the feed items. Other content could be videos, photo galleries or even google maps.
Its a cool little free feature and can be added to any site with one line of code which is a reference to a custom script. You can customise the pop up from the snap website and change the colour of the background image, whether or not to show the icon, upload a logo and whether the pop-up is used for internal links as well as external ones.
You can also choose to do what I have done which is let the add-on automatically scan the page for links it thinks it can generate content for rather than hand crafting them. All in all a nice little add-on.