My friends and I actually use a tax advisor based in the US that has a lot of experience with US tax laws for Expats working abroad. My contact is called Pam Smith.
They are good, fast, most things can be sorted via their online tool and/or phone and they are very reasonable price. Some of my friends did the "catch up" filing and with their help, it was done quickly and without any penalties.
Koutoulas & Relis, LLC
Certifiied Public Accountants & Consultants
1776 N. Pine Island Road Suite 316
Plantation, Florida 33322
(954) 332-1345
Fax (954) 332-1346
ps@krcpas.us