There's a new CRAN mirror available: cran.revolutionanalytics.com. It's provided by Revolution Analytics and hosted at Rackspace's high-availability data center in Dallas, TX. Especially for R users located in the western US, using this mirror will provide high-bandwidth access to open-source R downloads and CRAN packages while taking the load off of the main cran.r-project.org server. The mirror is updated nightly (just after midnight, Pacific time).
To have R use this mirror for package, add the following line to your .RProfile file (or create one in your home directory or R working directory):
(By the way, if you were already using the mirror cran.revolution-computing.com, it now redirects to cran.revolutionanalytics.com.)