You gotta try CoolIris

Thanks to Lifehacker I have today installed a new Firefox extension that is the coolest I have found in a long time. With Cooliris (which actually works with either Firefox or IE) running, when you hover over a link on a web page, it will open a preview window showing the new web page. But it’s not just a preview window – it’s fully interactive. If you decide you’re really interested in the page, there’s a button so you can open the page in a new tab. There’s also a button that will allow you to email the link to a friend.

I’ve played with CoolIris for just an hour or so but I’m really digging it. It’s customizable; you can disable it for certain domains, control what action (hover, CTRL-hover, click, etc) will open the preview, etc. It’s worth trying. Go check it out.