Quick script made back in early 2014 with Python.
Automated message sending on Facebook via the browser.
It's based on Selenium, a web browser automation tool. You can find out more here.
You can install the Python selenium package with pip install selenium.
Selenium expects you to have Chrome installed in the default location for your operating system. You'll also need to make sure that you have the required ChromeDriver executable and that its path is properly made available to WebDriver. See Google's ChromeDriver site for details.
Run the script in any shell with python main.py on a system with Python installed/configured.
Follow the prompts to input user information, desired messages, message quantity, and time interval data.
Finally, let it run!