The best cover I found is the
Incipio Kaddy Folio, it was already mentioned here a few times. Still waiting for it but I really like the simplicity and system of it. Seems the best way to secure the Kindle to the cover by far, no hinges or straps.
I posted today on the review of the cover but I thought I should post here too, to let you know that they now have 4 more color, those new colors come in a new material (synthetic leather) but the price is the same. The other 2 (in nylon) are still available.
By the way, it seems that it's best to order from the original website because Amazon seems to have a backlog of 1 to 3 months to ship it, at least for me. In the product reviews one person said that ordering for incipio.com wouldn't have that problem.
I love the red one

that's the one I ordered BTW.