From the post:
www.R-fiddle.org is an early stage beta that provides you with a free and powerful environment to write, run and share R-code right inside your browser. It even offers the option to include packages. Since a couple of days it’s gaining more and more traction, and was mentioned on the frontpage of Hacker News.
We designed it for those situations where you have code that you need to prototype quickly and then possibly share it with others for feedback. All this without needing a user account, or any scrap projects or files! We even included a very-easy-to-use ‘embed’ function for blogs and website, so your visitors can edit and run R code on your own website or blog. This is the first version of R-fiddle, so do not hesitate to give us feedback.
Working together with the help of R-fiddle
You can use R-fiddle to share code snippets with colleagues when tossing around ideas, in order to find that annoying bug, or by making your own variations on others people code. It’s easy: Just go to http://www.R-fiddle.org, type your code, and get your public URL by pressing ‘share’. This is a lot easier for your potential troubleshooter/colleague/.. since (s)he can immediate run and check the code, save it once finished and share it again. So by sharing your R-code through R-fiddle, you can not only help others to better understand your code, but they can also help you!
Using R-Fiddle in a distance education context, especially on data mining with R, will benefit both instructors and students.