Invoicera is the best billing application that we have used. It is very easy to use and has got a host of features. I've found Invoicera to be a very nice application for small businesses. It helps me to have better control over my finances, and cash flow management.
Very easy to navigate with all the features of online invoicing/billing, tracking, expense management, estimate management, etc. I was looking for complete invoice management and staff management solution, which I found in Invoicera. This invoicing software also allows me to integrate payment gateways and accept debit and international cards for transactions. Above all, it is easy to use and mobile-friendly.