QuickChart - free and opensource service to generate a chart image from URL
DO_Snapshot - command-line snapshot maker for your DigitalOcean droplets.
MetaBase is the easy, open source way for everyone in your company to ask questions and learn from data.
MailHog - Web and API based SMTP testing, inspired by MailCatcher
Localstack - a fully functional local AWS cloud stack. Develop and test your cloud apps offline!