For vBULLITEN forums you should try this : http://www.vbulletin.com/forum/showthread.php?277280-How-to-display-latest-threads-in-HTML-PHP-page NOTE :It is not as good as DIGITAL POINT SPY
There is a couple ways to do it, in both cases your going to need to use AJAX, I recommend using jQuery to make life easier. After that you just need to query the db and post it out at a set rate, then pull more data once you run out, but insure that its not the same data. I assume you do not know there is a vbulletin add-on that does the DP spy, in fact I'm sure it is the same thing: http://www.vbulletin.org/forum/showthread.php?t=127013