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.
FreshBooks - The ideal accounting software for small business owners.
ChargeOver - ChargeOver automates recurring billing, subscription billing, & payment acceptance. A SaaS that integrates with Xero, Quickbooks, & has an API. Free trial.
ZipBooks - ZipBooks is online accounting software for small businesses. 100% free, forever.
MinuteDock - Web-based time tracking software designed to integrate with the Xero accounting package.
Zoho Books - Smart Accounting for Growing Business