For freely-redistributable Linux documentation, see the Linux Documentation Project sites at ftp://sunsite.unc.edu/pub/Linux/docs/LDP/ and http://sunsite.unc.edu/LDP/
Stay tuned to the news:comp.os.linux.announce newsgroup for further developments.
At least the following anonymous ftp sites carry Linux.
Textual name Numeric address Linux directory
============================= =============== ===============
tsx-11.mit.edu 18.104.22.168 /pub/linux
sunsite.unc.edu 22.214.171.124 /pub/Linux
ftp.funet.fi 126.96.36.199 /pub/Linux
net.tamu.edu 188.8.131.52 /pub/linux
ftp.mcc.ac.uk 184.108.40.206 /pub/linux
src.doc.ic.ac.uk 220.127.116.11 /packages/linux
fgb1.fgb.mw.tu-muenchen.de 18.104.22.168 /pub/linux
ftp.informatik.tu-muenchen.de 22.214.171.124 /pub/comp/os/linux
ftp.dfv.rwth-aachen.de 126.96.36.199 /pub/linux
ftp.informatik.rwth-aachen.de 188.8.131.52 /pub/Linux
ftp.Germany.EU.net 184.108.40.206 /pub/os/Linux
ftp.lip6.fr 220.127.116.11 /pub/linux
ftp.uu.net 18.104.22.168 /systems/unix/linux
wuarchive.wustl.edu 22.214.171.124 mirrors/linux
ftp.win.tue.nl 126.96.36.199 /pub/linux
ftp.stack.urc.tue.nl 188.8.131.52 /pub/linux
srawgw.sra.co.jp 184.108.40.206 /pub/os/linux
ftp.denet.dk 220.127.116.11 /pub/OS/linux
NCTUCCCA.edu.tw 18.104.22.168 /Operating-Systems/Linux
nic.switch.ch 22.214.171.124 /mirror/linux
sunsite.cnlab-switch.ch 126.96.36.199 /mirror/linux
cnuce_arch.cnr.it 188.8.131.52 /pub/Linux
ftp.monash.edu.au 184.108.40.206 /pub/linux
ftp.dstc.edu.au 220.127.116.11 /pub/linux
ftp.sydutech.usyd.edu.au 18.104.22.168 /pub/linux
tsx-11.mit.edu and fgb1.fgb.mw.tu-muenchen.de are the official sites for Linux's GCC. Some sites mirror other sites. Please use the site closest (network-wise) to you whenever possible.
At least sunsite.unc.edu and ftp.informatik.tu-muenchen.de offer ftpmail services. Mail email@example.com or firstname.lastname@example.org for help.
If you are lost, try looking at http://sunsite.unc.edu/LDP/HOWTO/Distribution-HOWTO.html, where several distributions are enumerated. Red Hat Linux and Debian appear to be the most popular distributions at the moment, at least in the U.S.
Most people now install Linux from CDROM's. The distributions have grown to hundreds of MBs of Linux software, and downloading that over even a 28.8 modem or an ISDN connection takes a long time.
There are essentially two ways to purchase a Linux distribution on CDROM: as part of an archive of FTP sites, or directly from the manufacturer. If you purchase an archive, you will often get several different distributions to choose from, but support is generally not included. When you purchase a distribution directly from the vendor, you usually only get one distribution, but you usually get some form of support, usually installation support.
There are many BBSs that have Linux files. A list of them is occasionally posted to comp.os.linux.announce. Ask friends and user groups, or order one of the commmercial distributions. A list of these is contained in the Linux distribution HOWTO, available as http://sunsite.unc.edu/LDP/HOWTO/Distribution-HOWTO.html, and posted regularily to the news:comp.os.linux.announce newsgroup.