Dolibarr
Dolibarr is a modern ERP & CRM tool and easy to use Windows PC software package to manage your business! Customers, invoices, orders, products, stocks, agenda, e-mailings, shipments.. all in one great suite program!
Also, this model allows us to have a very large end-users base, so It can enhance the user interface from a lot of feedback. This is an important factor why Dolibarr (DoliWamp) is known to be the easiest ERP and CRM of the market.