I made my voyage from Excel to R more than 5 years ago and learned mostly by trial and error (and reading the R manuals). Most people don't prefer my approach of "keep at it until you figure it out", so I don't have a lot of personal advice to share. My main piece of advice is that the best way to learn R is to use it, so most of the resources below focus on "how-to" do certain things in R.
While R for Windows comes with a very basic GUI (I'm not familiar with the R for Mac OS X GUIs), most people will want and benefit from something more elaborate. The GUIs below were taken from the R GUI Projects page (visit the page for more information / alternatives) and I added the newcomer, RStudio:
Blogs / Videos
- The Climate Charts & Graphs blog has a video to help help Excel users get familiar with R, a list of R resources, and--most impressive of all--a toolkit to help Excel users move up to R.
- The Decision Science News blog has two video tutorials (part 1, part 2) to help people get started using R.
- J.D. Long, a fellow economist, has compiled a list of R resources on his blog, Cerebral Mastication.
I haven't read these two books personally, but I've heard very good things about both of them. Both focus on how to accomplish specific tasks with R.