Unless the site has an XML or RSS feed you can leech from, it will require some trickery. Either with complex JavaScript, or a server side scripting language like PHP (the idea being that you load their content quietly and parse it for information, then display parts of it).
Here's an example of a script I made to return the number of google search results for a keyword, using PHP+JavaScript. The parsing might be outdated though, since google made a few changes to their search results.
Fetch Pages Indexed with PHP and JavaScript