Yes,you can always ask those webmaster that have unuse traffic to direct to you. AFAIK,many proxy site have traffic that they don't want,so its good idea to contact them.
free ways to get traffic press releases article marketing forums video marketing social media (twitter, myspace, facebook) classified ads (backpage, craiglist, kijiji)
i can assure you that if you want huge traffic and that too FREE, start commenting on blogs related to your niche....i have tried this myself and the result was positive