Another quick command line utility thing, this time to copy the contents of a file onto your clipboard without having to use the mouse (this is on Ubuntu, with the bash shell, incidentally).
First install xclip:
sudo apt-get install xclip
Now make an alias for xclip with the flag that directs the clipped contents to the clipboard:
alias xc='xclip -selection clipboard'
(you can also put this line in your ~/.bashrc file)
Then you can put stuff onto your clipboard with this:
cat aFile.txt | xc
and paste with the usual keystrokes (CTRL-Shift-v on Ubuntu).