Yoast - Yoast offers plugins to improve SEO and optimize web sites and blogs.
Typeform - Create beautiful, next-generation online forms with Typeform, the form & survey builder that makes asking questions easy & human on any device. Try it FREE!
Jackmail - A newsletter plugin for Wordpress.
Survey Monkey - Create and publish online surveys in minutes, and view results graphically and in real time. SurveyMonkey provides free online questionnaire and survey software.
Wordfence - Comprehensive security plugin for WordPress.
Google Forms - Simple web forms from Google.