Signpost.com&#x27;s backend was Lisp. Originally, when the company was named Postabon.<p>I know because I worked directly with their cofounding CTO, Shaneal Manek, during the early buildout phase. I wrote their launch iPhone app, and it talked to a web service Shaneal made, in Lisp. Our app was featured on live TV during some morning business news segment, major network. It was pretty exciting. Anyway they later shifted the feature set and, I believe, rewrote the backend in Java, after Shaneal went to Greplin. Pure speculation for the rewrite was because it was considered as being easier or &quot;cheaper&quot; to find Java devs. Though I&#x27;d argue a sharp&#x2F;solid engineer can work in any language, and Shaneal was definitely that.<p>I&#x27;d suggest also that perhaps the biggest strategic win was that the combination of our slick iPhone app and the Lisp backend with the CxO&#x27;s pedigrees all helped them to eventually land investment from Google Ventures. Runway and eyeballs are king.<p>I also worked at Orbitz as a senior engineer back when they used ITA and ITA had not yet been bought by Google. So I can +1 confirm on what is probably the most famous commercial application of Lisp.