I've been renting a house for about a year now in Newport News, Virginia without a lease agreement. If I decided it was time for me to leave do I owe the landlord anything? Does he have any claim to charge me further rent or can he take me to court somehow and say I can't leave?

This is America. Your landlord cannot force you to stay if you don't want to stay.

However, you will have to pay, unless, before you move out, you you give the landlord due notice, typically 30 days.

You are considered a month-to-month tenant. In Virginia you have to give the landlord written notice at least 30 days prior to the next rental due date.

You can read more about it at LIS > Code of Virginia > 55-248.37

No you just can't leave without any notice. Even without a written agreement there are landlord tenant laws that govern. Just as your landlord can't just throw you out without going through a legal process, neither can you just up and leave.

However, you only requirement is 30 days notice. Though it is 30 days prior to when your rent is due. If rent is due on the first, then you have to give 30 days prior to that date. If you don't give notice, you will owe rent for that time