My library is getting too large. I'd like to remove the videos so I can manage them separately. I suppose if there was a way to sort the library by media type, then I could drag all the videos to a folder then delete them.
Create a smart album inside iPhoto with multiple criteria (iPhoto unfortunately can't create smart albums based on Kind).
Then flag them all with a unique keyword (e.g., DELETE). Go to Photos under Library and search for that keyword.
Throw away everything you find.
@bahamat's solution works, but there's a more robust and convient solution - tested on iPhoto '11, but presumably also works on earlier versions.
Further notes (optional reading):
I think you can do this in Finder. If you open a finder window, you may be able to use the built-in search functions in there.
For example, you should see a list of a few folders on the nav bar on the left that are kind of purple in color - those are saved searches and I believe they'll show you content from within iPhoto. There's also the built-in spotlight search box in the upper right-hand corner of your finder window (and another master one for the system in the top right). That may help you.
I'm pretty sure spotlight has everything it needs to give you search results for exactly this very quickly. Of course, this depends on you having something like OSX 10.4 or whenever spotlight was released. It is cool that it'll show stuff from within iPhoto. At least, it does for me on Snow Leopard.
Anyway, I can't test as I don't have a mac handy. Good luck