Neal Caren's (UNC) data scraping/processing tutorial. Potentially a useful teaching/learning resource?
Handy info on branching and merging with Git.
Hadley Wickhams's GitHub page for his advanced R development courses. Includes useful material on advanced programming in R as well as package development.
Markdown package for the R statistical software environment. Handy for publishing R code (e.g. to Rpubs) and for integrating latex, comments and other text more seamlessly into code.
Project page for google-blockly, which looks a whole lot like Scratch, just without all the fun kids stuff.
A set of blogposts making the case that Unix can be used as an IDE. Also describes a bunch of handy commands and a conceptual approach to Unix that even non-Unix-as-IDE users can appreciate.
Yet another Git tutorial that proved useful to me at some point.