I found an older article on the Google Reader blog where they post a great bookmarklet: It displays feeds referenced by the current page and allows you to preview them in Google Reader. Convenient for their users, and a great building block for a more generic tool.
I've modified their code in a number of ways -- the most obvious change is that the bookmarklet-generated links will point directly to the respective feed URLs, not to a Google Reader preview page. Then there are some cosmetic changes (I didn't like their choice of generated markup), but not much else.
Here's my version:
I'll be using this bookmarklet a lot -- Safari's handling of the <link>-tag is not very convenient, and I've just about enough of manually looking for feed links, be it on the page or (frequently also) in the HTML source.
Chris Wetherell of the Google Reader team states in their aforementioned article that this will not work in IE6 with SP2 -- I haven't tested on any IE. FF and Safari work fine.
Update: 2006-03-16 -- made some small changes to the code.
Update: 2006-03-17 -- fixed a text color bug on some sites. Slightly shorter code.
Update: 2006-03-19 -- fixed another text-related bug on some sites. Some refactoring -> even shorter.
Update: 2006-11-18 -- Marjolein Hoekstra extends this into an OPML Auto-discovery Bookmarklet, cool idea! The accompanying article also has a great explanation of the process of feed discovery, and on how to make your OPML auto-discoverable, so it's definitely a recommended read.