I recently started experimenting with Keynote on my iPad. I have a custom video which I required to be shown in the presentation, however Keynote on the iPad only allows to import images or videos from your Photo Stream or Camera Roll. This means that you either need iTunes to synch the movie to your iPad or get creative. The latter is my choice, as I don’t have iTunes installed.
In order to be creative, your iPad needs to be Jailbroken and you need the excellent iFile app from Cydia. By using iFile, you can upload your video/image to the iPad using the web interface. After upload, navigate to your file and view it.
Press the 
And voila, it is now available on Keynote. Happy presentations.
See also: http://iphone.heinelt.eu/?Applications:iFile:File_Viewers