This article presents a Web 2.0 approach for the arrangement of peer tutoring in online learning. In online learning environments, the learners' expectations of obtaining frequent, one-to-one support from their teachers tend to increase the teachers' workloads to unacceptably high levels. To address this problem of workload a self-organised peer allocation mechanism is proposed for the easy arrangement of instant tutoring by fellow students. The approach is based on a computational model which selects the most appropriate peer from a population of learners. A software prototype has been developed and tested with learners in two different educational settings. The evaluation shows that the use of a self-organising, synchronous peer-allocation system is not self-evident. It may be successful, but context variables have great impact on its functioning. Although the system technically functioned appropriately, students often appeared to use alternative ways for asking for help. In view of its potential for the efficient arrangement of distributed online support recommendations are given for successful appliance of the approach. (Contains 2 figures.)