I like the Marware cover best as offered by Amazon here:
http://www.amazon.com/Marware-Eco-Fl...3&sr=8-1-fkmr1
It has a solid feel, can be propped up by the flip on a desk for easy reading, has a flap where one's fingers can secure for reading away from a desk and closes solidly with a wrap around elastic to secure it.
The kindle 3 is firmly enclosed on all sides with openings for operating all controls and ports.
Finally, it does not have the 2 hooks which could cause problems in some covers.