Just to add:
In the past, if you were using a private delivery service (FedEX, DHL, etc.), the address for the Austin Center was different.
Internal Revenue Submission Processing Center
3651 South Interregional Highway 35
Austin TX 78741
USA
Attention: Receipt and Processing
Telephone: (512) 460 7944
The 2012 information for 1040 still instructs you to search on the IRS site for the address. This year, I can find no reference in Publication 54 to 'private delivery services'.
Per 1040i, to view the instructions, you need to go to the IRS site and type 'private delivery service' into the search box. For some reason, you can not bookmark the page with the addresses. (It doesn't have an updated URL.)
I am
assuming the above address is still correct (something to check out before June 15). Any more precise knowledge welcome!
IRS at the London embassy still showing this addresshttp://london.usembassy.gov/irs/irsoffice.html