As I was writing some code today in R, I realized how there are a few sites that I am constantly going back to for help. Thought I'd share some of those quickly.
Dates and times in R - Anyone who works with temporal data for long quickly realizes how difficult dates and times can be to a programmer - especially when dealing with it in Excel. I generally use POSIXlt or POSIXct formats with my data, which are detailed in this link.
R graphics - par arguments (mar, oma, mgp) - R is incredible for creating figures/graphics/visuals as it is highly flexible and you can control every detail. It is also very frustrating because you DO have to control every detail, and finding the relevant code is often difficult. This article is a great for understanding how to control margis and axes in your plots, which is nice not only for cleaning up individual plots, but for when you want to start combining multiple plots into one file.
Cookbook for R - This site is a great resource for many aspects of R and I'd recommend it as a good place for beginners to start. What I use it for, however, is its info on the 'ggplot2' package, which is a very popular package for developing intuitive graphics (I tend to switch between ggplot2 and base graphics, depending on need) - see the 'Graphs' portion of the website for these examples. Most basic plot types are included here, as well as separate sections on axes, text, and a very handy "multiplot" function for combining plots in ggplot2 into a single file.
As I come across other good resources I'll try to put them in quick posts. I'll also try to make a post in the future regarding my favorite packages! In the meantime, happy coding!