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.
EspoCRM - EspoCRM is open source CRM (Customer Relationship Management) software that allows you to see, enter and evaluate all your company relationships regardless of the type.
ChargeOver - ChargeOver automates recurring billing, subscription billing, & payment acceptance. A SaaS that integrates with Xero, Quickbooks, & has an API. Free trial.
CiviCRM - A Constituent relationship management for the Civic Sector
Elorus - A super-easy online invoicing & time tracking software
Less Annoying CRM - A simple customer relationship manager made just for small businesses. Manage contact info, track leads, and never miss a follow-up.