There is an excellent overview of the history of Linux and a whole lot more at LinuxTraining.pdf which is well worth reading and using for reference on many Linux things.
Sometimes you can end up pulling your hair out with the differences between the flavours of Unix, Linux and Mac OS X, in which case Rosetta Stone for Unix is a very useful site.
I have not tested this but Linux Antivirus Scanner | Free Antivirus for Linux Tool Download | Sophos would be a good Anti-Virus scanner for Linux.
www.centos.org - The Community ENTerprise Operating System
Red Hat | The World's Open Source Leader
Linux OS | SUSE Linux Enterprise
UNIXhelp for users
PuTTY: a free telnet/ssh client
WinSCP :: Official Site :: Free SFTP and FTP client for Windows - support SCP from Windows as well as SFTP