I've been looking at many free tools but have not yet found what I am looking for. The tool needs to be webbased, programmed in PHP with MySQL as backend.
The features need to be easily accesible and contain a management system of client data, orders made by them (no fixed products) and reoccuring orders, so I get warned when I need to sed out the next invoice.
Cool, but not really needed, is a client side, where clients can see what orders they have running, which invoices are not yet payed, etc.

There are many such tools at SourceForge, but I have not yet found one that does what I want, without the hassle of larger programs.