The $1 Kindle 4 Cover (amazopia.com)

This is good, but I've been using a $12 moleskin reporter style notepad with a back pocket.

Tear out half the sheets, and the notebook holds the tablet perfectly, plus you still have a note-pad you can use. The elastic at the bottom keeps it closed. The pocket tore at the bottom, but a bit of duct tape solved that.

Classier looking than an envelope, but super cheap and functional.

Well, we pay for looks.

I own this (now) $6.50 leather cover, which looks decent and cost me only $15 a few months ago.

http://www.amazon.com/CE-Compass-Cover-Kindle-Black/dp/B004A...

I think I paid £2.50 for a black neoprene 'hoodie' cover. It will last forever.