Voiceflow - Build voice apps in your browser without coding
API to bot - Convert your API to Alexa skill or Google Home app in 5 mins
Alexa for Business - Using Amazon Alexa’s voice enabled devices for workplaces
BotTalk - Create Alexa skills and Google Assistant actions with Markup
rasa NLU - A set of high level APIs for building your own language parser
Voice Principles - Guiding principles for voice design, all in one place