mkdir / rmdir	To make (mkdir) or remove (rmdir) directories.
cd	To change to a new directory.
ls	Lists the files and directories in a directory .
ls -l	Lists your files in 'long format', which contains a lot of useful information, e.g. the exact size of the file, who owns the file, who has the right to view it, and when it was last modified.
ls –lrt	Lists your files in 'long format', in order of time stamp, and reverse order.
rm	Remove files.
more	Shows the first part of a file, as much as will fit on one screen. Just hit the space bar to see more or q to quit.
cat	Shows the entire file on the screen.
head	Shows the first couple of lines of a file on the screen.
tail	Shows the last couple of lines of a file on screen.
grep	Find lines that match patterns in files.
mv	Rename or move a file.
cp	Copy a file to a different name or location.
pwd	Shows the directory path you are currently in.
ln -sf	Makes a symbolic (-s) link (ln) of a file. The file will appear to be in two locations, but is only physically in one location. (The –f option ensures that if the target file already exists, then it will first be unlinked so that the link may occur correctly.)
nedit	Simple file editor.

 

If you want more information, try these web sites:

http://mally.stanford.edu/~sr/computing/basic-unix.html
http://pangea.stanford.edu/computing/unix/shell/commands.php
http://www.math.harvard.edu/computing/unix/unixcommands.html
http://www.washington.edu/computing/unix/unixqr.html
http://www.kb.iu.edu/data/afsk.html
http://en.wikipedia.org/wiki/List_of_Unix_utilities
http://www.cs.colostate.edu/helpdocs/vi.html