Apple’s iPad Camera Connection Kit provides an SD reader and USB input for your iPad. Now there is a third party option for that provides the same SD/USB reader or a separate CF/USB reader. This is great for pro shooters who use cameras like the 5D MkII or 7D which use CF cards.
Unfortunately, the iPad currently doesn’t allow you to edit HDSLR video footage in iMovie. iMovie only accepts up to 720p 30fps footage which comes from iOS devices. Hopefully Apple will update this in the future or someone will make an app that can edit HDSLR footage.
You can still view and edit photos and backup video files to your iPad.