Email Marketing

• Mailchimp (//www.mailchimp.com) - Email auto replies, drip campaigns and newsletters.
• Aweber (//www.aweber.com) - Email auto replies, drip campaigns and newsletters.

User Engagement

• Qualaroo (https://qualaroo.com/) Pop-up quick question and capture replies about why people aren't converting.
• Olark (//www.olark.com/) Engage in real time chats with landing page visitors to ask them real questions.

A/B Testing

• Optimizely (//www.optimizely.com)
• Visual Website Optimizer (//www.visualwebsiteoptimizer.com)

Analytics

• Google Analytics (//www.google.com/analytics/)
• Kissmetrics (//www.kissmetrics.com)
• Mixpanel (//www.mixpanel.com)

User Testing and Surveys

• Five Second Test (//fivesecondtest.com)
• UserTesting.com (//usertesting.com)