Bitrix24 is free ERP with CRM created specifically for sales oriented organizations.
It is available both in cloud (free) and on premise (paid), with open source code access. The CRM module is extremely powerful and comes with a number of sales tools, including full sales cycle management (lead to deal), email marketing, contact center (telemarketing), quotes and invoices, workflow automation, mobile CRM and more.
Bitrix24 ERP manual and online training videos are available here and here.
For a free online demo, self hosted Bitrix24 30 day trial or customization/integration requests, please contact Bitrix24 partner in your region directly.