There are some wireless external hard drives that can be used with the iPad.
The Kingston Wi-Drive, which costs $50 for the 16 Gigabyte, and then $30 more for every 16 gigs more. It works by you turning it on and then accessing the files on it from an app that you download on your iDevice. You can access music, movies, and other stuff. No connections or anything, it works like a WiFi connection, you connect to it from the setting on the iPad under wireless networks.
Then there is the Seagate GoFlex, which some would recommend over the Wi-Drive. But this one costs $199 and had 500 Gigabytes of storage. It works the sameway as the Kingston: no wires, runs over its wireless connection. You can actually fit up to 300 HD movies on it.
Theoretically yes, use the camera connection kit to import them. There are catches to this.
First, I've literally had a 50/50 success rate with flash drives, so you'll need to experiment.
You'll have better luck with SD cards.
You do have to follow the strict naming convention. Put the files in a folder named DCIM and give it a name of exactly 8 characters.
You will not be able to see the names of the files so you'll have to guess which one to import. Also, you can't watch from the SD card or flash drive, you have to import it onto the iPad then watch and delete, so while it can save room, youi'll have to have the room on the device in the first place.