I would also like to know how i can place ads into my rss feed? Mashable and Techcrunch always have the same banners in their feed. Also, shoemoney's ads (even his fan page ad) are always connected to google, but is this adsense or is this independent from google? Thanks
To place ads in rss feed, choose the Adsense for RSS option in your Adsense account. That will guide you how to migrate your RSS to Google, and subsequently start showing ads in it.
It's actually called Adsense for Feeds Your feeds will have to be redirected through Feedburner, so you will probably have to promote the change so that your current subscribers get the new feed. But yup, that's what you do. It's easy.