Envoice - Send invoices and get paid on Paypal, Payoneer, Stripe and Square.
Free Invoice Generator - A free invoice generator for startups
Invoice Ninja - Invoice Ninja is a free, open-source solution for invoicing and billing customers.
Invoice Maker - Generate your invoices online for free
Invoice Bus - deliver all your invoices, price quotes, follow-ups, and thanks notesautomatically
Billdogg - Beautifully simple invoicing for freelancers