Loopalyzer offers a big collection of free loops under Creative Commons CC BY 3.0. This license allows you performance and standard use but you need to give attribution to Loopalyzer. To simplify you can give credit just with:
Video loops by Loopalyzer (www.loopalyzer.com) licensed unde CC BY 3.0
And where to place this? Well, depends of the use you will give them. It could be at the end of the credits of a video clip, in a Youtube video description, in a flyer, in a party website, on your Facebook page…be creative!. This way I get promotion, I´m happy so I make more free clip, you get more free clip. We all are happy. There is a dayly limitation of downloads to avoid server saturation. Right now its limited to 2 downloads a day, that will be raised in the future.
Too much trouble? Yeah, I know. These free clips have a lower price than commons content, so you can purchase them in a normal way or with a subscription and not to worry about attributions and download limitation.