Go to this site, its self explanatory.
http://bluray.liesinc.net/#bruk
Your machine is region A because you bought it in the USA. Machines in Europe/Australia are region B. The above link shows which movies from region B will work in your player. Just look which ones you want, go to sendit.com and purchase it with peace of mind.
Its probably not applicable to you, but Japan is also region A (same as the USA). Although movies in Japan cost a hell of alot more than in the USA and its common to find language issues etc.
At the moment, there is about 4 or 5 good movies available in the UK which will work in your player that are not released in the USA. Its not a great deal, but it opens things up a tad if you run out of movies to buy in the USA.
Enjoy.