I would like to list some R resources that I personally believe are great to learn. I would also list out a few resources which are good to follow everyday for any R enthusiast.

• http://tryr.codeschool.com/
• https://www.datacamp.com/
• http://swirlstats.com/
• http://www.computerworld.com/article/2497143/business-intelligence/beginner-s-guide-to-r-introduction.html
• http://data.princeton.edu/R/default.html

• Coursera
  • https://www.coursera.org/course/rprog
  • https://www.coursera.org/specialization/jhudatascience/1?utm_medium=courseDescripTop
• Udacity
  • https://www.udacity.com/course/ud651
• EdX Platform
  • https://www.edx.org/course/kix/kix-kiexplorx-explore-statistics-r-1524

• R Cookbook
• R in a nutshell
• 25 recipes for getting started with R
• Data Mining and Business Analytics with R (advanced)

• http://r-bloggers.com/
• http://www.r-statistics.com/
• http://onertipaday.blogspot.in/ - You can follow them via their twitter handle @RLangTip
• http://blog.yhathq.com/ - Some of their blog posts are many things that you could do in R
• http://www.rdatamining.com/ - Advanced and very informative website

• R reference card - http://cran.r-project.org/doc/contrib/Short-refcard.pdf
• Lubridate package cheatsheet - http://blog.yhathq.com/static/pdf/R_date_cheat_sheet.pdf
• R Markdown cheatsheet - http://shiny.rstudio.com/articles/rm-cheatsheet.html
• Shiny cheatsheet - http://shiny.rstudio.com/articles/cheatsheet.html
• data.table cheatsheet - https://s3.amazonaws.com/assets.datacamp.com/img/blog/data+table+cheat+sheet.pdf

• R Studio - A fantastic IDE for R.
• Deducer - Deducer package
• R Commander - Rcmdr package
• Rattle - Rattle package
• GrapheR - GrapheR package

There are a few very important blogs that you should go through once you start working with R. Here are a few:

• http://blog.yhathq.com/posts/10-R-packages-I-wish-I-knew-about-earlier.html
• http://blog.revolutionanalytics.com/2013/09/top-languages-for-data-science.html

• If you are using 'for' loops in R, then you are doing it wrong. http://nsaunders.wordpress.com/2010/08/20/a-brief-introduction-to-apply-in-r/
• If you don't like R help, try this. It's fantastic. http://rdocumentation.org
• Write a R package - http://hilaryparker.com/2014/04/29/writing-an-r-package-from-scratch/

• http://google-styleguide.googlecode.com/svn/trunk/Rguide.xml - R coding conventions by Google.