Actually this is old stuff (2006), but it got lost in a comment section. I think this can still be useful to some and I also post this here for prosperity.
Somewhere in 2006 my colleague Lucas Jellema wrote a post on the AMIS Technology site about querying rss feeds from the database. My colleague Anton Scheffer and I commented on that article with our XMLDB functionality mindset. Later on in 2007 Lucas wrote another useful post called “Querying RSS feeds in SQL…“. Peter Wolf commented that he had also written a very nice blog post about using XMLDB functionality while Integrating Yahoo Pipes into APEX.
I think this is still useful stuff to a lot of us, although you should keep in mind that the table(xmlsequence(extract())) construct will be, in time, out lived by the XMLTABLE function. Also XMLTABLE supports XPath V2, the table(xmlsequence(extract())) doesn’t. The XMLTABLE function is available from Oracle database version 10.2.