Landing Pages in MailChimp - Easy to build, custom landing pages for free
Ethereal by HTML5 UP - A fully responsive side-scrolling one-page HTML5 template
Viral Loops for Startups - Virality for startups made easy 💪
TemplateMo - TemplateMo is a great place to get bootstrap templates from your website, which are all HTML5 supported with CSS layout.
Carrd - Simple, responsive one-page site creator.
UIdeck - Landing Page HTML Templates and UI Kits