I had reviewed billing software named APlusbill few months back. The product does not have an attractive user interface and lacked many features. Hence, I was searching for another alternative product which can automate my daily task and I managed to find WHMCS. It is a powerful product developed using PHP and runs under MySQL, but can be installed under both Windows and Linux environments. The vendor has specially developed the software for those who run web hosting business. However, it can also be used if you sell other products like templates, themes, etc. The latest version 2.3, which I reviewed, contains lot of improvements and bug fixes compared to previous versions.