Update (Jan 30): uploaded a better screenshot.
Another way to use RSS technology for advertising purposes is to put ads on the client software instead of the content. Nothing conceptually new here, of course, as the ad-supported software has existed forever, but this particular implementation is interesting.
InClue developed a reader plug-in for Outlook that displays a contextual ad along with the content. CEO of the company writes: "We allow media publishers to pre-load RSS feeds, get metrics and revenue share for each new inclue! user they create."