The only rss feed provided is for entire posts not a listing of posts and looks like this when added to a public page:
http://wb2-web.sharepoint.com/Pages/blog.aspx
If that's what you want, take the rss feed link from the bottom of the posts page, convert it to javascript at http://feed2js.org and embed it using this generator and a Paypal gadget.
All in all though, O365 just isn't built to include SP content on a public site and you'll find it much easier and get better results at another venue.
