$6000 in every month from a single blog
 

http://www.stevepavlina.com/blog/

http://www.problogger.net

I think it is the http://www.problogger.net/.
But I have never known for certain if he made the money he claims he did.

If you look around his blog you will see that he has a lot of blogs, not just one.

i think this shows the importance of focus, as now-a-days people run 20 sites that will make them a $1 a day, they spend so much time trying to dedicate time to all the sites.
That the content is either rushed or poor, There is'nt enough quality time gone into 1 site.
This is an example of person dedicating all efforts and time into makeing that 1 site a success.