I wrote a blog post about three years ago about doing single-sign-on stuff between salesforce and google by writing a google appengine app that acted as a SAML IDp. At the time, salesforce didn't speak OAUTH and google didn't natively speak SAML, so you had to do it on your own. I put it on an old blog I had laying around and turned on google adsense.

To date, I've made $6.31 from that blog post alone. Someday, I'll get over $100, so adsense will pay out.