ASCII art.

Make ASCII logo.

figlet:

$ sudo apt-get install figlet

$ figlet "Hello world"
$ figlet -f slant "Hello world"

With spaces between letters:

$ figlet -k -f shadow "Hello world"

sysvbanner:

$ sudo apt-get install sysvbanner

$ banner Hello

cowsay:

$ sudo apt-get install cowsay

$ cowsay Hello
$ cowsay -f duck Hello

To get list of available cow picture file:

$ cowsay -l