Well, yes, free knowledge IS what the Internet brings us, but here are some free online learning opportunities:
MIT OpenCourseWare publishes all of their course materials. For free. Special section for high school instruction and subject index available.
iTunes U offers If you’re an iTunes user, you’ve probably seen the mortarboard icon that links to free iTunesU content online.
although the search feature wasn’t immediately apparent to me–still trying to figure this out as a non-avid iTunes user.
WorldLectureProject indexs video of mostly professors’ lectures atworld lecture project; among the other CreativeCommons learning resources is the searchable index of
DiscoverEd–showing an example of curriculum and teaching resources tagged with poverty, although I found this site to not be limited to adult learning.
GOOD Magazine recently ran a list of sources for free class materials including ccLearn’s index, and WildApricot publishes a monthly list of non-profit webinars.