BillGrid.com - BillGrid is an easy to use online invoicing, billing and expense management system that will save you time with tracking clients projects, expenses, invoices and payments.
Zoho Invoice - 100% free online invoicing software for small businesses.
ChargeOver - ChargeOver automates recurring billing, subscription billing, & payment acceptance. A SaaS that integrates with Xero, Quickbooks, & has an API. Free trial.
Bookipi - Clean, simple way to save money with an app
Elorus - A super-easy online invoicing & time tracking software
Simple Invoices - Never Wait For Clients To Pay You Again!