StartupBase - Community of makers & early adopters
Product Hunt - A website that lets users share and discover new products
PitchWall - Browse new startups, and submit your mobile app/games startup's beta page here.
Betafy - Where startups meet beta users!
Beta Family - 50,000 testers to test your app
BetaList - BetaList provides an overview of upcoming internet startups. Discover and get early access to the future.