If you are looking for a Financial Management program, then Quckbooks is pretty much the definitive standard, whether you use it directly or you have other software that exports just the financial data to Quickbooks. Now, if you are looking for something that does more than that, you may be looking for a program known as CRM (Customer Relationship Management), Job Management, Task Management or Production Management, for which there are many options that are designed specifically for the sign industry like Cyrious, ShopVox, Printavo, Sign Tracker, PrintSmith, etc. or generic like CoreBridge, Trello, Zoho or many others. If you are any good at working with software to create your own system, you could use a database program like the excellent Filemaker Pro or even Microsoft Access.