Which address to use on taxes?

This might seem like a really basic question, but there are no stupid questions, right? 

This year will be my first time filing taxes whilst living over here. It should be relatively straight forward since I worked in NYC until October, and have not worked over here at all in 2006.

My question is when I fill out my taxes, should use my 'US address' (my mother's house, where all of my bank statements/other US mail go, still have a valid license in the state, etc, lived there again briefly before moving here) or should I use my address in London? Is there anything wrong with using one over the other? Any advantages to using one over the other?

Sorry if this seems obvious, and thanks in advance for any advice.

This is a GREAT question and I'm looking forward to seeing the answers!! I'm in the same boat, but I have one additional question. My house in Maryland is now my rental property and my parent's address that I use for mail and such is in Pennsylvania. I'm not a resident of PA and I haven't lived there for many years, but because that's now my "US address" and all my mail goes there, it's the address at my bank, etc., am I required to pay PA taxes as well as Maryland??

You can use any address you like. 

Benefits for London address: solidifies your position that you are an expat.
Benefits for your Mum's address:  more permanent than your London address, so if there's a later IRS audit or other correspondence, it's more likely to reach you.

As you did not give up your drivers license and have some ties to that state, you may wish to use your London address as one of many steps you must undertake to solidify your position that you are no longer resident in that state.

Thank you Lizzit. I just wanted to make sure I didn't do anything wrong.