9.1 CTAN

CTAN is the Comprehensive TeX Archive Network, a network of ftp servers where you can get (almost) every thing that is related to TeX. CTAN has three backbones
Germany
ftp://ftp.dante.de/tex-archive/
UK
ftp://ftp.tex.ac.uk/tex-archive/
USA
ftp://ctan.tug.org/tex-archive/

and several mirrors. You can obtain a list of the current CTAN mirrors as
ftp://ctan.tug.org/tex-archive/CTAN.sites

Many of the servers (and at least the backbones in Germany and the UK) support compression on the fly, i.e. you can download the contents of a directory and all its subdirectories as a .zip of tar.gz file. Simply add the suffix .zip of .tar.gz to the URL of the directory to download.

There is also a searchable index for CTAN at
http://ctan.tug.org/cgi-bin/ctan-web-search
and
http://www.dante.de/cgi-bin/ctan-index