What cloud computing applications exist? What programming languages were used to create them?

Silly answer: "Cloud computing" is a ten-dollar term on a nickel errand! :)





Seriously: All it means is that the software you used to have on a computer is now on the Internet and accessible through your web browser. The other case is a web application that offers a new service that you wouldn't have had without the web, but it's so easily accessed that it feels like just another program on your computer. Some examples:





Google apps, BitTorrent, Amazon Mechanical Turk, SQL Services, and, oh, yeah, many Yahoo apps!





For instance, you can bookmark links in your browser, but what do you do when you want to use a different computer, or easily share links with your friends? So we have Delicious.com, where you save your bookmarks "in the cloud". Now all you need to access your bookmarks from any computer in the world is your Delicious.com log-in. What you used to have installed locally is now done remotely.





As for what programming languages, any browser-based or server-based language is likely to be used. Javascript, PHP, ASP, AJAX, Perl, Java, SQL...