Odoo

Odoo is a modular, open-source business suite that spans far beyond ERP into CRM, website, e-commerce, HR and manufacturing. The entry price is the lowest of any system in this directory and the app model lets a company start narrow and add modules over time. The trade-off is that depth varies sharply by module, and the community edition shifts more responsibility onto the implementation partner - hosting, upgrades and third-party module vetting all become the partner's job. It is underserved by existing directories, which means partner discovery is genuinely harder than for the Microsoft or Oracle channels.