Entrecard is more than a directory and a way to get your blog known in the blogosphere for free if you take the time to be active and get known on the forums.
We have two blog directories where you can make free submission of blogs http://www.blogdirectory.ws http://www.blogwebdirectory.com
Like any promotion it is only 1 way and it is best to cover a few angles that work for you. that way if one drops of the others fills in. But yes this system works From memory i wrote we went from 4 + million to 800 K in alexia a while back, we are now below 500 K mainly with this method only and have just started to add some extra promotion. It might sound a tall order but i am gunning for under 100 K with mainly just this as the back bone then spreading out from there. Yes it is free but you can also throw a few $ into it as well it's your choice, and it helps to keep your pending ads as full as you can as people take some time to approve.