This is something Zalewski has written about: http://lcamtuf.blogspot.com/2010/10/http-cookies-or-how-not-... --- if this kind of thing is interesting to you, his latest book, _The Tangled Web_, is excellent.
I was particularly stunned to learn HTTP Cookie headers can clobber 'secure' cookies set over HTTPS. Eye-popping.
Also: take a crack at the CTF we set up. I think (a) you'll do well at it and (b) it'll be fun to watch you. http://microcorruption.com.
Anyway, the list is not even close to real solution (just had long discussion with @titanius on twitter why not). So many quirks and use cases of <sub>.domain.
> it'll be fun to watch you
uh. hmm, ok.