Portable Keyboards from Amazon.com
Pianos are great, but when you want a bit of variety of sound or you need to produce sound in different locations, hauling around a piano is a bit of a pain. That's when a portable keyboard is handy. You can get a variety of keyboards to suit your needs from Amazon.com.
A full-size keyboard has 88 keys, and these are great when you want to give an impromptu performance outside or need to travel around with a keyboard. They closely mimic the full range of a piano, and some even come with weighted keys. Digital pianos are close to full-size keyboards, but these typically have better sounds albeit with a narrower range of potential instrument sounds.
Most portable keyboards have 61 keys. This is a reasonable tradeoff between size and range. These portable keyboards typically have a large number of sounds and instruments to choose from, so you can produce some fairly impressive tunes just from one instrument. They're a little too large to be carried on your back, however, so they're not always good when you're walking anywhere.
Finally, you might want to consider a 49-key portable keyboard. This is often the smallest size of keyboard that offers a decent range of sound and practicality. These are also good for those starting out on the keyboard, as these are some of the cheapest keyboards available.
For those who want a piano substitute and don't mind how big they are, an 88-key portable keyboard is likely the best option, and there are some really good ones by Roland and Korg that are well worth considering. For those wanting a general keyboard to tinker with or wanting a little more portability, a 61-key portable keyboard is usually ideal, and Yamaha and Casio are some solid brands. A 41-key portable keyboard is good if you're starting out or looking for the ultimate in portability.