There’s one new class, but almost all the standard classes are exactly the same. Here are a few notes anyway, though.
Artificers: Artificers specialize in making items, magic and non. They can’t cast any spells, but they can infuse items with power temporarily, or spend more time to make a permanent magic item. They have the ability to fiddle with traps and other devices just like thieves do, and have enhanced abilities to work with magic items. This is a new class for the setting, and I can provide more information about it if desired.
Clerics: Clerics can choose to worship the Silver Flame (the national church of one of the countries, it’s sometimes accused of bordering on the inquisitorial, especially in reference to the great lycanthrope purge of 50-odd years ago), the Blood of Vol (if they’re from Karrnath), the Sovereign Host (a general pantheon of nine gods worshipped by most everyone else, unless they’re a cultist), or a specific god in the Sovereign Host. Note that in Eberron, clerics can be of any alignment — the gods don’t interfere with daily life and don’t send down visions, so there is nothing to prevent a cleric from being overzealous and shifting into evil behavior). Here’s a good post on enworld talking more about religion in Eberron.
Druids: Druids go way, way back. In olden days they were defenders of the world against creepy things from other dimensions. These days they’ve factionalized to a certain extent, and no longer present a united front. Here are some of the larger sects:
Gatekeepers: Carry on the old tradition of keeping the world safe from other planes and undead.
Wardens of the Wood: Your basic druid, these guys are into nature and stuff.
Greensingers: These druids have a special tie with the fey and the mystic powers of nature.
Children of Winter: These druids are into the death-and-decay part of the cycle of life, and do their best to bring it about. They have special ties to vermin and other creepy not-quite-animals.
Ashbound: These are the ecoterrorist druids — they hate mages and farmers and hunters and do their best to scour them from the earth.
Druids also get animal companions depending on their choice of starting terrain.
Monks: Monks can take feats to let them multi-class normally, and use a few other snazzier weapons as monk weapons.
Paladins: Halfling paladins can ride dinosaurs for their special mount, of course.
Rangers: Some rangers are associated with the druidic sects mentioned above. The same rules on animal companions apply also.