Many hackers are starting to create mash-ups using a new program called Greasemonkey. Say what? This add-on software to the Firefox Web browser allows software "scripts" to be installed on the browser that customize the way a Web site looks and works on that particular computer. Among the hundreds of free scripts now available for download is Book Burro, created by grad student programmer Jesse Andrews.
Once installed, Book Burro senses when you're browsing an online bookstore and automatically searches several Web bookstores to find the best price on the book you're viewing. One might assume it's the last service Amazon wants to help, but it actually featured Book Burro on its Web services site for outside programmers.