Billdogg - Beautifully simple invoicing for freelancers
fish shell - The friendly interactive shell.
Free Invoice Generator - A free invoice generator for startups
zsh - The Z shell (Zsh) is a Unix shell that can be used as an interactive login shell and as a powerful command interpreter for shell scripting.
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
PowerShell Plus - Learn how to learn and master PowerShell fast with an interactive learning center, a powerful IDE, pre-loaded scripts, and a PowerShell Editor… all for free.