Gnutella is not a 'site' ! Gnutella is a network of p2p (peer to peer; sharing from person to person). So when you do a search you are finding files shared by people like yourself, perhaps even your next door neighbour or person across town.

Just be wary of Spam. Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see)

Phex has a size filter to apply to search results so you can filter out anything less than a certain size for videos. Most but not all video movies will be above 500 MB in size.