Alexa Skill Kit - Effortless Alexa Skill development with AWS Lambda
Google Open Source - All of Googles open source projects under a single umbrella
BotTalk - Create Alexa skills and Google Assistant actions with Markup
LaunchKit - Open Source - A popular suite of developer tools, now 100% open source.
OK Google - Explore over 150 Google Now voice commands in one place
Open Source @IFTTT - A collection of IFTTT OSS projects.