[Osiris]

A number of dedicated search engines have been launched this year. The latest one I have discovered is uLinkx that allows you to search for videos from multiple (Youtube, Myspace, Google Video, Yahoo etc) in one place.
One of the nicest features of uLinkx is that video results can be watched within the site, without having to click away. An RSS service is available, so you can easily monitor your favourite searches. Results can also be bookmarked and grouped into playlists for easy retrieval.
More: uLinkx