There is a site called Ads Black List. Basically the idea behind it is that it provides you with a list of low paying advertisers that you can put into Google Adsense’s competitive ad filter.

So for example if site xxxx.com only bids as high as 2 cents, then chances are (this is how their theory works anyway) if you add xxxx.com to the competitive ad filter on adsense you should start earning more money.
A small selection from one of their lists are as follows:

best4sites.net
infoscouts.com
finditonline.ws
searchguide.biz
truelocal.com
info.com
cohit.com
expert-expert.com
tunu.com
getbestinfo.com

…

But what I don’t get is how it would actually improve your earnings. Firstly, there is a maximum of 200 filters you can put on your adsense competitive adsense filter, so that chance that one of the domains in the generated lists would actually appear on your adsense block is quite low (in my opinion) (apart from maybe ebay.com which seems to get in every list…). Also, as far as I am aware (and I am sure this is 100% true, other wise “bidding” higher on adwords wouldn’t make sense…) only the highest paying ads are shown. If you have room for 12 ads (3 x block of four ads), only the 12 higest paying ads will be shown.

So if you ban site xxxx.com, another one will be shown, chances are that you will earn even less with that ad that replaced the xxxx.com advert.

Maybe I am not seeing this site as I should be, but it doesn’t make much sense to me (hey, its early in the morning [and I appologise for this post if it doesn't make sense...]) although to be fair I havn’t tried it out. Maybe if someone who has tried it out could comment about it?