Create and Manage Invoices with Zoho Invoice
In a nutshell, Zoho Invoice lets you create, send, and track invoices and estimates. All you do is add customers, define your products or services, and then create an invoice. When that's done, you can e-mail, print, and/or export to PDF. There's even an optional "payment gateway" that lets you accept payments from customers via PayPal. If you're a Zoho Project user, you can generate a customer invoice based on an existing project. Zoho promises integration with Zoho CRM and other apps in the future.
The free version of Zoho Invoice lets you create up to five invoices or estimates per month. Plans range from $5-35 monthly for more volume. From what I've seen so far, this is an extremely polished and easy-to-use solution for any small business looking to simplify and automate invoices.