Shoptopus: Invoice Generator

Great app, simple to use and very easy to customise for different countries or requirements. In less than five minutes you will have a good looking professional invoice, packing slip, etc. Some niceties like an integration with the accounts page or notification email make it easy for the client to download previous invoices, saving you time. For many this app would be all you ever need for invoicing.

Exceptional backup from the team behind it, I needed a small change and it was all done within a couple of hours of requesting it - in Australian time!