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.
FreshBooks - The ideal accounting software for small business owners.
fusebill - Fusebill is the leading recurring billing and subscription management software for businesses. Try Fusebill for subscription billing made easy!
QuickBooks Online - QuickBooks Online is a Cloud Accounting for small business that can be used on iPad, mobile phone or computer to do invoicing, billing, run reports, or even pay employees online.
MinuteDock - Web-based time tracking software designed to integrate with the Xero accounting package.