This paper describes a cost-effective infrastructure for building ubiquitous collaborative learning spaces. It uses techniques from the Semantic Web and ubiquitous computing to build a learner-centric service-based architecture to transform existing traditional learning spaces (e.g., classrooms, computer labs, meeting rooms, and hallways) into intelligent ambient learning environments. This is achieved by blending a number of inexpensive technologies which are optimally configured to provide services that can perceive a learners' location and schedule, identify current learning activity, recommend learning resources, and enable effective real-time collaboration and resource sharing between learners and their instructors. These services are semantically defined and homogeneously integrated using a shared ontology, service policies, and inference rules. Service invocation and coordination are triggered at runtime by context-changes in the learning environment, thus offering full context awareness and providing real-time support for various learning modes, including formal, informal, and Ad hoc collaborative learning. Furthermore, the learning is supported by a range of mobile devices that are commonly used by learners to enable better instruction and communication. A prototype system is developed and tested using different learning scenarios. The system has also been tested by a group of learners whose feedback is provided for performance assessment.