If you are on Ubuntu, please see this README for Ubuntu from CRAN --- it will allow you to get to the current version of R (today 3.0.2, in a few days 3.0.3) with mininal effort.
Once you have a current R version, getting the doBy package (which depends on it) installed is a piece of cake too.
If however you prefer to stay with your version of R, you can manually fetch an older version of doBy from its CRAN archive. Download to, say, /tmp
and run R CMD INSTALL
by hand on it.