Apart from the well-known GMAT sites like clearadmit.com,accepted.com, hellaslist,totalgadha etc etc I came across a couple of sites that I've not heard of before. These turned out to be really good , esepcially the site mbapodcaster.com. This site has a huge inventory of podcasts , mostly interviews of experts. This is promisingly useful to both beginners as well as post-MBA folks.
Also useful was http://mbaleague.blogspot.com/