I. Getting Around
cd (1)		- change working directory
ls (1)		- list contents of directory
cp, ln, mv (1)	- copy, link or move files
chmod (1)	- change mode
mkdir (1)	- make directories
rm, rmdir (1)	- remove files or directories
file (1)	- determine file type
find (1)	- find files

II. Looking at your stuff
more, page (1)	- view a file one full screen at a time
less (1)	- opposite of more
cat (1)		- concatenate and print files
tee (1)		- pipe fitting
head (1)	- give first few lines
tail (1)	- deliver the last part of a file
pr (1)		- print files (not necessarily to a printer though)
lpr (1)		- send a job to the printer (BSD)
lprm (1)	- remove jobs from the printer queue (BSD)
lp, cancel (1)	- send/cancel requests to the LP print servicei (SYSV)
lpstat (1)	- print information about the status of the LP printservice(SYSV)
grep (1)        - search a file for a pattern
awk (1)         - pattern scanning and processing language
diff (1)        - differential file comparison
sort (1)        - sort and/or merge files
uniq (1)        - report or filter out repeated lines in a file

III. Editing your files
sed (1)         - stream editor
tr (1)          - translate characters
wc (1)          - word count
ispell (1)      - correct spelling for a file
spell(1)        - find spelling errors
vi  (1)         - screen-oriented (visual) display editor based on ex
emacs(1)        - GNU project Emacs

IV. Whats going on around you
date (1)        - print and set the date
du (1M)         - summarize disk usage
env (1)         - set environment for command execution
kill (1)        - terminate a process
ps (1)          - report process status
pwd (1)         - working directory name
stty (1)        - set the options for a terminal
tty (1)         - get the name of the terminal
who (1)         - who is on the system

V. Mail and stuff like that
mail, rmail (1) - send mail to users or read mail
write (1)       - write to another user
talk (1C)       - talk to another user
mesg (1)        - permit or deny messages
(t)rn,nn,tin (1)- read news
finger (1)      - display information about users
biff (1b)       - give notice of incoming mail messages

VI. 
passwd (1)      - change login password and password attributes
chfn (1)  	- change "finger" info 
chsh (1)  	- change shell