As Big Boss said look on Blu-ray.cm. Howerver they don't region test everything. Some tiltes might have "A (B and C untested)" in the tech info for a title.
It's very hard for them to test for region C as that's Russia and Russia don't allow their players to be sold outside the country. When I worked for Testronic Labs we had to have a Region C PS3 for that reason. The only way we got one was one of our testers was Russian and I think she got it some how.
It's annoying that the packaging is never truely clear and you can't always trust it. FYI WB are all region free.
If you look on blu-ray.com and you like having the best version of a BD available with the most special Feature, packaging and so on then blu-ray.com is very good at showing you all the versions for any title. Set the search engine to look for Theatrical from the links above the search bar, search any title and you should get the movie poster. Scroll down and you should see all the releases currently available from the different countries. You should see the BD releases on the left and bundles if they are from a boxset on the right. Also if there are any UV versions and even the DVD releases.
Most of the info about non US versions for UV, Digital copies, DVDs and so on comes from us users.
One good example for searching the best version is the film Buried. Most of the releases have a cropped version. They made it 1.78:1 instead of the original 2.39:1. It's not a case of they removed the blanking to reveal more picture. They pan an scaned it. The US version is only reagion A though so I can't get that one but the Dutch version comes in a Metal Pack and says it's 2.39:1. I took my UK version back with disgust half the picture is missing.