R-Cookbook.com is a collection of "recipes"--problems, solutions, and working examples--contributed by the R community in order to share code, promote the use of R, and make the learning process more efficient for new users.
The site features: an interactive code display (in progress), recipe ratings, community tagging, multi-level RSS feeds (user-specific feeds, tag feeds, etc.), a recipe box to save users' favorite recipes, similar recipe recommendations, community-assisted guide creation (a linear organization of recipes), discussion forums, private messaging between users, and much more!
Registered users will be allowed to rate recipes, add their own recipes, take part in discussion in the forums, message other users, and save their favorite recipes.
If you are new to R, you might want to start with the Introduction to R and its "Further Resources" chapter, although the guide itself is a work-in-progress.
About the site
The site has been developed using the Drupal CMS framework. I've only had a tinker with the code a bit in developing the site, which speaks for the quality of Drupal, and its associated modules. I created a module for the site called HighligheR, which I'll be extending in the near future to be even more interactive in the way it displays R code.