To cite Rcpp in publications use:

Dirk Eddelbuettel and Romain Francois (2011). Rcpp: Seamless R and C++ Integration. Journal of Statistical Software, 40(8), 1-18. URL http://www.jstatsoft.org/v40/i08/.
Eddelbuettel, Dirk (2013) Seamless R and C++ Integration with Rcpp. Springer, New York. ISBN 978-1-4614-6867-7.

Corresponding BibTeX entries:

  @Article{,
    title = {{Rcpp}: Seamless {R} and {C++} Integration},
    author = {Dirk Eddelbuettel and Romain Fran\c{c}ois},
    journal = {Journal of Statistical Software},
    year = {2011},
    volume = {40},
    number = {8},
    pages = {1--18},
    url = {http://www.jstatsoft.org/v40/i08/},
  }
  @Book{,
    title = {Seamless {R} and {C++} Integration with {Rcpp}},
    author = {Dirk Eddelbuettel},
    publisher = {Springer},
    address = {New York},
    year = {2013},
    note = {ISBN 978-1-4614-6867-7},
  }