[R] Contributed packages

[Vadlamani, Satish {FLNA}]

Folks:
If you wanted to find out about what are the contributed packages and classify them, how would you go about it? For someone new like me, I would like to know what the possibilities are. When I click on "install packages" on my Windows version of R, it gives me a list but it is hard to figure out from that list what is the purpose of each package and to what class it belongs (for example, class of regular expressions).

What is the equivalent of CPAN.org for Perl in R where you can browse Perl modules by category? Thanks.
Satish