RSS auto-discovery is a neat idea. Shortly after the original spec was published a profusion of bookmarklets to auto-detect an RSS feed, and subscribe you to this or that aggregator service flourished.
However, this evening, as I collected urls for my own aggregator service, I’m unable to find a bookmarklet that simply finds a site’s RSS feed, without trying to lock you into a particular service. So, standing on the backs of giants, an RSS auto-detect bookmarklets, that merely returns the url of the RSS feed. As usual, drag the below link to your link toolbar to install.
It supports both the old and new formats of the auto-detect standard the third website I tried (boingboing) was still using the earlier spec.