The famous websites provide tons of useful information:

• Programming with Big Data in R
• Training of Remote Data Analysis and Visualization Center
• CRAN Task View: High-Performance and Parallel Computing with R
• Section "LAM/MPI/Rmpi" on R_note website
• Rmpi Tutorial by Acadia Centre for Mathematical Modelling and Computation
• Rmpi for R by Dr. Hao Yu

The famous book provides other parallel techniques in R:

• Q.E. McCallum and S. Weston (2011), Parallel R Data Analysis in the Distributed World, O'Reilly Media.

The famous mailing list provides a discussion group about high-performance computing in R:

• R-sig-hpc mailing list.