Yup, you can!
Here's how.
To invoke commands from within the shell:
:!<command>
Replace <command> with actual command, of course.
You can also use the output from the command line in your Vim file, you can use the read command.
:read !date
will output the date, like so:
Tue Jul 14 12:35:19 IST 2015
You can use this to convert coffeescript to JS, HAML to HTML, Markdown to HTML, etc.