jsonlite
A reasonably fast JSON parser and generator, optimized for statistical data and the web. Offers simple, flexible tools for working with JSON in R, and is particularly powerful for building pipelines and interacting with a web API.
In addition to converting JSON data from/to R objects, 'jsonlite' contains functions to stream, validate, and prettify JSON data. The unit tests included with the package verify that all edge cases are encoded and decoded consistently for use with dynamic data in systems and applications.
Example Use
library("jsonlite")
json <- '["Mario", "Peach", null, "Bowser"]'
# load json to dataframe/array/matrix (determined automatically)
fromJSON(json)