Pond5 is one of the many places where you can find stock video clips online. What’s a stock video clip? It’s a professionally shot video clip (usually) that you can use in your web videos…royalty-free. In fact, a lot of videos on the web are put together using only stock video clips instead of “original” footage.
Stock video clips usually run anywhere from $15 to $100, depending upon the clip. But Pond5 has just started giving away a free, high-definition stock video clip every week.
To receive these weekly clips, you just need to go to Pond5 and register an account (it’s free). And…you can register with Pond5 by clicking here.

http://www.stockfuel.com offers a similar deal. Worth a look.
Also http://www.visionmates.com provide great videos, this is not a stock site, but they are real creators
Pond5 is a decent stock media resource, especially for video. Please keep in mind StockFuel as well for your video stock media demands. Cheaper and easier to manage than most. Also, a decent amount of quality video stock files.