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I've been using a $30 option that comes with a bluetooth keyboard, the cheapest one I could find anywhere. I've had no complaints as of yet, it feels very sturdy.

iPad Keyboard Case

The reviews are very good, and it's also compatible with the HP Touchpad
 
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There are numerous options available. Logitech has a couple of recent entries with very good keyboards. Zagg was the first major brand and several others are now available with varying levels of quality of the keyboards.

One caution, however. If you're accustomed to a full size keyboard, or even a laptop keyboard on an 11" notebook you may find the keyboard/case combos to be very cramped. If you're an accomplished touch typist, it can be a major problem.

If that is a problem for you, consider the option of a separate keyboard case/stand such as the Incase Origami Workstation. The price of an Apple Wireless Keyboard and Origami Workstation is approximately the same as the Zaggmate keyboard/iPad combo case.
 
Zaggfolio

Are you happy with the Zaggfolio? Looking at this right now....any comments?
 
last week, i purchased a case with keyboard in it, but it too heavy for me to carry...its a leather one, i do like the design of the bag, but its too heavy.
 
So many cheap and good keyboard case with Bluetooth , it's $30 more or less as usual, you can google the information.
 
I just bought the Logitech Keyboard Case for iPad 2 by Zagg. So far I like the feel of the keys and don't mind the small keyboard. However, I really dislike the fact that it doesn't have an escape key. That's a major problem for me as I'm always using vi or emacs.
 
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