With the rapid advance of stand-alone e-learning systems, we believe a sharable and interoperable portal platform capable of integrating various existing learning systems is critical for the future development of e-learning systems. We highlight two problems as the root causes for current ineffective sharing of learning resources: learning object interoperability and learning activity interoperability. In this paper, we propose an open and interoperable e-learning portal architecture to solve these problems: 1) With regard to learning object interoperability, we propose WSRP+ service as an enhancement to WSRP standard to send presentation content and intercept crucial information from LMSs in order to facilitate the presentation-level integration of learning objects and keep the learner's learning status in our e-learning portal. 2) With regard to learning activity interoperability, BPEL4WS is used for the task-based orchestration of course workflows among shared learning systems, in which value-added tasks such as grading, evaluation, recording, etc., can also be integrated as a whole. At the end of this paper, we present our prototype implementation to illustrate the feasibility of our approach. (Contains 10 figures and 1 table.)