I recently bought a case for the regular Nook from Overstock.com:
http://www.overstock.com/Electronics...3/product.html
They seem to have a lot of these "silicone" cases, all with different prices. The one I got is one of the least expensive ($7.99), but reading the reviews it seems like it might be one of the best. Some reviews of other cases there say that they are flimsy and/or not well made. But the one I got (product #13088267) is very sturdy and thick, so it gives you a lot of protection (on the sides and back - the front is open), and it is nicely finished and smooth to the touch.
The silicone case covers the side buttons and the top on/off plate (the speakers and recharge plugin on the bottom are not covered), but it has raised buttons on it and is quite flexible, so when you push down the buttons below activate very nicely. In fact, the side buttons seem easier to push with this cover over them. I was worried that the top on/off switch might be operated by the cover even when you didn't want it to, but that has never happened. It works perfectly.
The one negative about this silicone case is that it is kind of heavy (much heavier than the flimsy "silicone" cases B&N sells for $20).