vim commands and piping

You may know that you can execute commands from inside of vim, with a vim command:

:! ruby do.rb

which will execute that code, and then - upon hitting enter, return you to your workspace.

Another nice one, is you can execute the exact same command with:

:!!

I use those a lot, but I just learned you can send the current buffer via a pipe (even if unsaved) into a command like this:

:w !sort

Pretty nifty, huh?