All of the XML content is accessed via the ".xml" action… To get RSS or RSS2 out of that (not viewable in most browsers), add ";type=rss" or ";type=rss2" to that URL.
Recent Posts (displays the most recent posts that you can see)
"Sub-action": recent
Default: Shows 5 most recent posts
Available options:
limit=x - display the "x" most recent posts (if number is less than 5, it will display 5. If number is larger than 255, it will display 255).
board=y - display only the recent posts from board "y"
Example: /index.php?action=.xml;sa=recent;board=72;limit=10
News (displays the first post from the most recent topics that you can see)
"Sub-action": news
Available options:
limit=x - display only "x" items
board=y - display only news topics from board "y"
Example: /index.php?action=.xml;sa=news;board=72;limit=10