Run it in Terminal with:
$ cd ~/Library/Safari
$ plutil -convert xml1 Bookmarks.plist
$ xsltproc SafariFeeds2OPML.xslt Bookmarks.plist > SafariFeeds.opml
$ plutil -convert binary1 Bookmarks.plist
The resulting file should import into your favorite newsreader.
[robg adds: I haven't tested this one.]

