When I discuss these devices with my friends, I usually say "eReader". They reply with "What's an eReader?". I say, "an eBook Reader" and again they say, "what's that?". Then I say, "you know, a Kindle", and that's when they understand.
Here's a scary thought - many people today refer to MP3 Players as "iPods". Maybe everyone will refer to eReaders as Kindles in the future.