E-Learning is a fast, just-in-time, and non-linear learning process, which is now widely applied in distributed and dynamic environments such as on the World Wide Web. However, it also poses three challenges to the systems that support e-learning. This paper present our on-going effort to develop an ontology-based framework for e-learning systems, which allows teachers to organize learning materials in a dynamic and flexible manner, and provides multiple ways for students to access the materials either by navigation, search or recommendation. A module that helps to classify the learning materials according to the schema of the ontology is also presented in the proposed framework.