www.instructables.com is a pretty decent diy site. Posts are owned by the person who placed them, so I would assume that there are at least a handful of GNU or CC licensed how-tos on the site.

Other than that I can’t think of any sites that focus on that sort of information and would have at least an allowance for copyleft license structures. If you find any, let me know, I would love to have some more to browse through.