The paper presents an evaluation method for e-learning platforms, based on different types of measurements collected in logs of interactions during learning sessions, and on the analysis of collaborative learning activities performed using social networks visualization of the relations established among users during the experiments. The evaluation was used to highlight the ease of access to different platforms' resources in two case studies: Sintec and Moodle. Problems encountered during the evaluation and possible solutions to be considered in future work (in the FP6 Cooper project) are also presented.