I have attempted to install knitr using RStudio. When I do so, this is what I get

 > install.packages("knitr")
also installing the dependency ‘evaluate’

trying URL 'http://cran.rstudio.com/bin/macosx/mavericks/contrib/3.1/evaluate_0.5.5.tgz'
Warning in install.packages :
  cannot open: HTTP status was '404 Not Found'
Error in download.file(url, destfile, method, mode = "wb", ...) :
  cannot open URL 'http://cran.rstudio.com/bin/macosx/mavericks/contrib/3.1/evaluate_0.5.5.tgz'
Warning in install.packages :
  download of package ‘evaluate’ failed
trying URL 'http://cran.rstudio.com/bin/macosx/mavericks/contrib/3.1/knitr_1.5.tgz'
Content type 'application/x-gzip' length 863862 bytes (843 Kb)
opened URL
==================================================
downloaded 843 Kb

The downloaded binary packages are in
    /var/folders/ym/flmt1pms5vj_wdhtsmwy63pm0000gn/T//RtmpWM2Yqc/downloaded_packages
> library("knitr", lib.loc="/Library/Frameworks/R.framework/Versions/3.1/Resources/library")
Error in loadNamespace(j <- i[[1L]], c(lib.loc, .libPaths()), versionCheck = vI[[j]]) :
  there is no package called ‘evaluate’
Error: package or namespace load failed for ‘knitr’

As a result, knitr does not work at all, even on the little test file provided. When I search the CRAN repository for OSX/Mavericks, I am not finding the evaluate package.

Am I doing something wrong; is there a workaround?

I cannot reproduce it. I can see the knitr package under http://cran.rstudio.com/bin/macosx/mavericks/contrib/3.1/

Alternatively you can install from source:

install.packages('evaluate', type = 'source')