I was just going to post about liking Mumford and Sons new album, Babel, but while making sure I wasn't double-posting a recommendation, found that it doesn't seem like much modern folkish stuff has been posted at all, so:

Mumford and Sons- (example (from new album)- Hopeless Wanderer)- These guys are the most popular of the genre, and get a lot of radio play (but they're good). If you listen to the radio at all, you probably have heard their song "Little Lion Man".

The Unseen Guest- (example- Let Me In)- Unseen Guest is a mix of Western songs with Indian instruments. Not quite "folk", but I like them enough to put them in this list anyways. They are the least known group in this list. They don't even have a website, or wikipedia page, so you can be all hipster. But everyone who gives them a try, loves them.

Eddie Vedder- (example- Rise)- Although well-known as the front man for Pearl Jam, Vedder's solo work has a different very down-to-earth sound. His two solo albums include the soundtrack for Into the Wild, and a collection of ukulele songs, called Ukulele Songs.

Ray LaMontagne and the Prairie Dogs (example- Empty)- Generic folk singer, but I still love it, and a folk list wouldn't be complete without it.

...I'll stop now.