The beautiful part of judo is that it depends alot upon the fighter to determine the style. However to go as a whole, you can probably break judo down into two major groups. (I along with many of you have never been to half these countries but this is what I can gather from watching competition tapes)
European: For some reason alot of people shun this but I like it alot myself. Basically most sambo wrestling type techniques get incorporated, and alot of very good stuff. More pickups, and basically when judo got popular in europe it changed the sport. Very physical judo
Japanese/Oriental: Generally more technique based, depending on the fighter can be more or less physical. But mostly known for high level of classical judo.
Japan is of course known for being the best in the world at judo, but keep in mind, judo is a sport of innovation, so anything can happen.