COOLIRIS (web browsing tool) This app's probably been around for a bit, though its fairly new to me. Basically, after installation, it gives your browser the ability to pop up a preview window of a web page for any link on a page, rather than having to click and go to the specific link. I prefer using it in FireFox since its a bit more customizable. For instance, I changed the default setting for "open preview on mouseover" to "open preview on mouseover icon". The default setting can be a bit annoying, since a window will automatically open should your mouse hover on any link.
Works rather well, especially for some news sites such as Google News and forums. You could open and read links without having to leave the main page. It's appears it's only available for Firefox, IE6 and MAC's Safari browser. Other browsers may have a similar add-on.