Several people (including myself) in recent posts have mentioned going to Amazon to check out what features a certain title has, be it for consideration to buy, for comparison to R3 counterparts, or just plain curiosity.
Although Amazon is generally correct, I've come to realize that Amazon's listing isn't entirely accurate. For one, they list many titles as RCE when in truth they're not. They list The Omen and Jaws 2 as barebones when in truth they are chockful of features.
Aside from Amazon, I suggest going to review sites like
DVDReview.com, and the movie's page at the
Internet Movie Database and click on "DVD Details" if there are any (sometimes there's not specially when the movie is new). It's far more comprehensive in listing features. It not only lists features for Region 1 but sometimes for Region 2 and 4 as well. A shortcut to go here is to just scroll down the movie's page at Amazon and you will see a link to it's page at the IMDB.