RabbitMQ - RabbitMQ is an open source message broker software.
Invoice.to - A simple & beautiful invoice generator with Stripe & Paypal
Ethereum - Ethereum is a decentralized platform for applications that run exactly as programmed without any chance of fraud, censorship or third-party interference.
Free-Invoice.co.za - Free Invoice Software | Free online tool that helps small businesses to generate free invoices and manage their contact list. It can be used as an alternative to expensive invoicing software and online invoicing applications
Hyperledger - Hyperledger is a multi-project open source collaborative effort hosted by The Linux Foundation, created to advance cross-industry blockchain technologies.
Free Invoice Generator - A free invoice generator for startups