Is there a service that let's me "send" bitcoins via email and doesn't require any account creation/login?
This is technically possible and can be easily implemented, but I see two problems, which may be stopping people from creating such a service:


Trust: how can the service ensure its clients that it will not
steal their money?
Security: email is not secure, a man in the middle can access the
email message on its way before the recipient, and steal the money.


If there is a solution to these two problems, there will be demand and implementations of such service.