OER Commons and MERLOT II have free content builders for the creation and hosting of lessons, courses, and other types of OERs. WordPress now offer an OER plugin.
Based on the type of OER, it may be more appropriate to add your materials to YouTube, Vimeo, Flickr or other websites for video/audio. You do not have to limit yourself to one platform
Adaption Guide (BCcampus) is a practical guide about how to customize — or adapt — an open textbook so that it better fits your needs in the classroom and elsewhere. See their Five rules of textbook development
Open Education Self-Publishing Guide (BCcampus) is a reference for individuals or groups wanting to write and self-publish an open textbook. This guide provides details on the preparation, planning, writing, publication, and maintenance of an open textbook.
Modifying an Open Textbook: What You Need to Know (Open Textbook Network) is a five-step guide for academics who want to modify an open textbook. Step-by-step instructions for importing and editing common open textbook file and platform types are included.
Authoring Open Textbooks (Open Textbook Network) Content includes a checklist for getting started, publishing program case studies, textbook organization and elements, writing resources and an overview of useful tools.
Creating and Modifying Open Educational Resources is a chapter-by-chapter informational tutorial for academics interested in creating or adapting open educational resources.