BetaList - BetaList provides an overview of upcoming internet startups. Discover and get early access to the future.
Targeted.io - Test your email designs across 30+ clients before you send'm
StartupBase - Community of makers & early adopters
Really Good Emails - A large collection of good product email design.
PitchWall - Browse new startups, and submit your mobile app/games startup's beta page here.
Stamplia - High converting and beautifully designed email templates