Installing R packages available for all users

Question

I have a few R packages installed under ~/R/i486-pc-linux-gnu-library/2.11.

I would like to make them, and any other R package I install from now on, a

Answer 1

aL3xa answer is wrong; you shouldn't expose those directories to write for all users.
Run R as a root (probably using sudo R) and then install packages as usual -- they will be placed in a global library and will be available for all users.