How to get your latest posts from vbulletin via RSS

You need to enable the External Data Provider in your vbulletin settings in order for this to work.

RSS2

Example: http://www.ozsource.org/forums/external.php?lastpost=true&type=rss2

RSS

Example: http://www.ozsource.org/forums/external.php?lastpost=true&type=rss

To display only new posts use external.php?newpost=true&type=rss instead.

Now how do you get this into wordpress?

Out of the box, WordPress can retrieve and pass an RSS feed. WordPress uses the MagpieRSS and RSSCache functions for parsing and automatic caching and the Snoopy HTTP client for the actual retrieval. See Fetch_rss.

A code sample to fetch your 10 latest posts:

<?php // Get RSS Feed(s)
include_once(ABSPATH . WPINC . '/rss.php');
$rss = fetch_rss('http://www.your domain.com/forums/external.php?lastpost=true&type=rss');
$maxitems = 10;
$items = array_slice($rss->items, 0, $maxitems);
?>