On those occasions when you are doing major maintenance to your site, it is nice to be able to put up a friendly message explaining what is happening and, more importantly, when your site will be available again.

You can read a bit more over at my WordPress Crash Test Dummy site where I used this plugin to leave a message while changing my site theme.

http://www.seedprod.com/

https://en-au.wordpress.org/plugins/coming-soon/

The best and most powerful free drag and drop form builder I have used. Easily add widget ready and responsive forms to your site. Beyond the basics, these forms provide conditional logic and variables so that you can create powerful solutions quickly. Add a running total to a list of items or calculate discounts on the fly.

http://calderalabs.org/

https://en-au.wordpress.org/plugins/caldera-forms/