Archive.org is a great place to find stock video footage. It is a little hard to navigate, but you will find some really unique stuff there, especially if you are looking for older public domain stuff. I actually shoot and offer stock video footage for free, and use that site to host the videos. I really do not want to risk spamming my site and violating the rules of this forum but obviously you'll see it in my signature. I WILL go ahead and suggest 2 other places I have found that offer footage for free:
Videezy.com and Videvo.net. Both are great resources for independent video makers.