Today, 2009-10-04, from http://cran.r-project.org/web/packages/ "Currently, the CRAN package repository features 1997 objects including 1993 packages and 4 bundles containing 15 packages, for a total of 2008 available packages." It was 1.5 years ago (2007-04-12) we were at 1000 packages, cf. https://stat.ethz.ch/pipermail/r-devel/2007-April/045359.html
From my previous in-house statistics there were ~500 packages in Oct
2004, and ~250 in April 2003. So, roughly, the number of packages doubles every 18 months. My daily procrastination /Henrik