For accounts that require passwords however, it may be that terms and conditions will dictate how an account can be transferred. I will be looking into this in more detail soon, so please check the blog for an update and some examples.
One easy method however, would be to ensure your executors get access to your passwords and account information. So long as this does not go against the terms of service, a service such as www.dataorganiser.com can store almost any personal information or data files so that your executors or family members can access the information after you die.