Soon Google will unleash its Google Code-In again where students age 13-17 swarm to mentoring open source projects and work on various small to medium sized tasks. Haiku will probably once again be part of it, as it was the past 6 years.
Tasks can range from documentation and artwork to PR, giving talks, writing guides or workshops, porting software and creating haikuports recipes, improving existing ports or native applications or creating new ones.
If you have ideas for tasks that may be suitable for students, please post them in a comment.