Just to let everyone know, GSOC (Google Summer of Code) time is nearing again. Last year, both Mahout and Solr had students and I think they did a good job. I'm sending this out to the dev lists so as to see if other people are interested in getting students to help on the various Lucene projects.
I have put in an entry for Mahout already for you to use as a reference.
For existing committers, If you are interested in mentoring, sign up on the Apache Wiki.