Amazon.com just added a new ad type for affiliate publishers -- they're called "Omakase" ads, and they seem to have some good potential.  You can find them by logging into your Amazon affiliate area, click on "build links", and you will see the new ad types at the top of the page. 

I know quite a few affiliates have given up on Amazon ads due to the somewhat low payouts, but these new ads should be tested anyway -- you may hit the jackpot on technology or consumer product themed pages.  Go ahead and try some of the optimization tips that are being used for other ad programs -- no borders on the ads, make the background the same color as your web page, hide as much of the junk as possible, and make the ads blend into your central page content as much as possible.  The closer to the center of the content, the better -- ads on the outside edges are clicked much less often.