David Smith points out a cheat sheet for dealing with strings in R:
The RStudio team has created another very useful cheat sheet for R: Working with Strings. This cheat sheet provides an example-laden menu of operations you can perform on strings (character verctors) in R using the stringr package. While base R provides a solid set of string manipulation functions, the stringr package functions are simpler, more consistent (making them easy to use with the pipe operator), and more like the Ruby or Python way of handling string operations.
Click through for a link to the PDF.