If you're using animations to capture attention, as opposed to illustrating a transition, for example, do not run the animation continuously. Run it for a short, defined period of time and then stop it. This keeps it from being a distraction on the page, while letting it perform its attention attraction function. Frames are excellent for keeping menus and other navigation choices in view, but they slow things done and have a negative effect on the ability of people to bookmark your page or print parts that they want. Almost all of the things that you would want to do using frames can be done using tables or other design options.
Frames are generally a bad idea.
Designers tend to like them so you may have to argue on this one, but users generally think they stink. There are some situations where longer videos for illustration or sampling purposes might be appropriate, though. If they are for you, make sure you use streaming video or audio technology such as Real Audio and that you use a service to set the audio or video up that knows what they're doing. Design for lowest common denominator browsers and connection speeds. In the current state of the art, that means the current AOL browser six months after introduction and the connection speed of 28.8.