DMPTool is free! It has "a click-through wizard for creating a DMP that complies with funder requirements. It also has direct links to funder websites, help text for answering questions, and resources for best practices surrounding data management."
Far more robust than our own starter guide, this DMP LibGuide from Colby College has TONS of information about data preservation, finding suitable repository solutions, links to best practices and recommended file formats, and much more.
While created to help researches in the UK, this site is "completely free to use and aims to provide you with everything you need to evaluate and implement those digital curation techniques most suited to your particular research project."