This website is very helpful if you need to delete your account somewhere and don't know how, because many providers do not want you do delete your account or simply do not care to tell you how you can delete your account.
You can just search on Accountkiller for the website from where you want your account to be deleted and you will be given short and simple instructions, so you do not need to search the whole internet.
Additionally all websites are either added to a black list or white list depending on how friendly or easy it is to delete your account there, websites and services that do not allow deletion of accounts at all are directly blacklisted. Sooner or later most accounts can be "deleted" these days, because they are legally required to, but you cannot be sure if they really deleted it.
So ideally before you create an account somewhere you check accountkiller.com, if that website is blacklisted and if it is you should consider not opening an account there to begin with, to save you the hassle later.