Mentoring is one of the ways in which it is possible to extend the sometimes sterile teacher-learner dyad of traditional (non-collaborative) approaches to learning.
MentorNet is a network for women in engineering and science. By mid-2003 they had already matched around 3000 students with volunteer mentors.
A system geared towards more traditional teaching settings is Profiler which allows individuals in a group to identify their points of strenth and weakness in a learning domain and to see who else in the group can be consulted for help with areas in which they are weak.