I can't feel at home without some good free Unix software. All the software listed here is used by myself and is an integral part of my Unix workplace. (This never finished list was compiled about 10 years ago when Linux workstations and servers were not so common and I worked mainly on Sun/Solaris and IBM/Aix workstations and servers).
Emacs the best Text Editor
It has everything: from language specific modes (for C, C++, Perl, Sgml etc.) to complete programmability. Without it I feel like a stranger, so, usually it is the second software I install on a new workstation (if automounting /usr/local is not an option).
Bash the Bourne Again Shell
The best shell in the world. This is the first software I install on a new workstation. Without it's filename completion and it's easily editable history mechanism I can't feel at home.
Elm the Electronic Mail reader
It's interface is text only and a bit outdated, it's not easy to MIME attach files to e-mails, but I am using it since 1989 and only in last years I found in Mutt a valid alternative.