I found SPA when I was looking around on the we-make-money-not-art blog. I noticed that when I hovered over the link text, instead of flashing up a wee text box, I got a small window with a preview of the site that the link would take me to, if I decided to click through.
I really liked this, and we're considering using something similar on the website I'm involved with at work, to allow people to look at definitions of unfamiliar words or jargon without having to move between pages. However, I'm wary as all get out about downloading code, especially when it comes with riders like this:
"6. Data Collection and Privacy. The Software may collect, store, and periodically send information back to Licensor or third party servers, including URLs accessed by the Software and search queries entered into the Software. In addition, the Software may automatically collect certain information during the installation process and/or indicate to our servers that you have successfully installed the Software. Use of certain feedback features in the Software may require you to submit certain personal information such as your name and email address. Licensor may retain and use for its own purposes all information you provide and all information generated from the operation of the Software (URLs, search queries, etc.). You agree that Licensor may use all such information internally for any purpose and may additionally transfer and disclose to third parties information (including your name, email address, Site domain, URL, and related content) for the purpose of approving and enabling your use or continued use of the Software, including to third parties that reside in jurisdictions with less restrictive data laws than your own."
So best you go to we-make-money-not-art to play round with this.