$ rss2xmpp.py feed-URL your-jabber-idOn the first run the script will complain that you have to put jabber settings in
~/.rss2xmpp. It writes an example for GoogleTalk there. Either RSS or Atom feeds should work.
The script itself is in the BitBucket: rss2xmpp.py.
BTW, I discovered, that BitBucket not only provides free OpenSource hosting for mercurial repositories, but has free SSH access and allows one private repository per account.