Creating multiple nested directories with one command

mkdir accepts multiple path arguments:

mkdir -p -- a/foo b/bar a/baz

To add to the above answers you can also do (in csh, tcsh, ksh, bash, zsh, fish, yash -o brace-expand):

mkdir -p /path/{to,a}/{lot,of}/directories

Reading the man page is always a good place to start.

The -p flag will create the required intermediate directories on the path.