All major consults have details about case studies in their career section.....
http://www.bcg.com/careers/interview...tice_cases.jsp
this one is from BCG career section....also tells u wht ur supposed to do in the case from a panel's perspective...
similarly in McK site too
cheers
suhas
P.S The cases here are prolly too involved vis a vis IIM GDs..
Forgot to add :- All of these are one on one thingie where in u can gather data continuosly by asking questions (huge weightages for kind of Questiosn asked/ assumptions made)...in IIM GDs as far as i know ull be given some data and u have to discuss under the four walls of these facts...dunno if u can turn around and ask panels further clarifications