doFuture 0.4.0 is available on CRAN. The doFuture package provides a universal foreach adaptor enabling any future backend to be used with the foreach() %dopar% { ... } construct. As shown below, this will allow foreach() to parallelize on not only multiple cores, multiple background R sessions, and ad-hoc clusters, but also cloud-based clusters and high performance compute (HPC) environments.
1,300+ R packages on CRAN and Bioconductor depend, directly or indirectly, on foreach for their parallel processing.
future 1.3.0 is available on CRAN. With futures, it is easy to write R code once, which the user can choose to evaluate in parallel using whatever resources s/he has available, e.g. a local machine, a set of local machines, a set of remote machines, a high-end compute cluster (via future.BatchJobs and soon also future.batchtools), or in the cloud (e.g. via googleComputeEngineR).
Futures makes it easy to harness any resources at hand.