MCMCvis, created by lab PhD candidate Casey Youngflesh is now peer reviewed and published in the Journal of Open Source Software! JOSS is journal that focuses exclusively on scientific software. While I think most would agree that giving software developers credit for their work is important, I think the practice of citing R packages (at least in ecology) is relatively rare. I (Casey) myself am guilty of this, to be sure. Cite the R packages/other software you use – publications and citations of those pubs are the currency of academia!