FreshBooks - The ideal accounting software for small business owners.
Xero - Xero is online accounting for your small business.
Avaza - Beautiful Projects, Timesheets, Expenses, Quotes & Invoices for Small Businesses
Wave Financial - Award-winning financial software designed for entrepreneurs.
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.
Fanurio - Time tracking and billing software highly appreciated for its simple project-based interface, flexible timer and detailed invoices. 15-day free trial.