If you play classical piano and want an electronic device, I would recommend something like the M-Audio Prokeys Sono 88 (which has internal sounds but also works as a midi controller) or the M-Audio Keystation 88es. If you're used to a real piano, you'll definitely want an 88-key device as the smaller ones simply are too crammed for proper piano-playing. I personally own the Prokeys Sono 88 and I am quite pleased with it. I got it with M-Audio's SP-2 sustain pedal, which has a really nice feeling to it. The keys on these devices are semi-weighted, which takes some getting used to, but in the case of the Sono 88, the keys are certainly acceptable. There are also hammer action devices, but they tend to be very heavy and bulky and portability was an important quality for me when I decided on what to buy.
