I'll try to post a ton of different bands, maybe you'll find something you like. Most of this is probably considered indie I guess, but there's some pretty good stuff here. Alphabetically listed even..
Arcade Fire: I'm pretty sure they're fairly well known, but if you haven't they're definitely worth a listen. They've got their own sound for sure.
Cloud Cult: This is really an amazing band, you should listen to some of their albums. I found nearly every song on 'Feel Good Ghosts' were songs I wouldn't get tired of, and 'The Meaning of 8' is a solid album. Not so much a fan of their earlier work - they have some good stuff but there's lots of experimental stuff going on too.
Human Highway: I have the feeling HH isn't as well known, but it was formed with members of the band 'Islands', another great band if you haven't heard of them. The album, Moody Motorcycle has a reeaally relaxed/mellow indie sound to it, it's great for relaxing...
Islands: As I mentioned, this is another really good band.. although I prefer the album 'Arm's Way' as there's a larger amount of really-good-songs on it. Definitely worth a listen.
Jose Gonzalez: Amazing classical guitarist.. his songs have a Spanish/Latin feel to them, and are mostly all just acoustic guitar and vocals, but his voice is what really makes him so good. It's mesmerizing :p Great skill too... check it out if you like acoustic stuff. I recommend the song "Crosses".
MGMT: I would go on about how good their experimental/alternative stuff is but I saw you already listened to them. To anyone else reading, GO LISTEN.
Sea Wolf: Hmm, they're not bad. Definitely on the quiet side, I don't like listening to them for too long because even though their music is really well written after listening to the album it makes you feel a bit depressed. I would still recommend listening to them... the song "You're a wolf' was used on a Chevy Malibu commercial, so it might sound familiar.
Sparkadia: Wow, I don't really know what to call this. It's... good, mostly. Kind of a weird pop/rock/indie thing going on that makes me think of a weird sort of Coldplay/Arctic Monkeys cross in some of their songs. It's a mixed bunch, but the first few songs off 'Postcards' are good. I hear their earlier work sounds depressing, while in Postcards the music itself sounds brighter but the lyrics are a touch dark.
The Spinto Band: Again, I've got mixed feelings about this band, but you should take a listen to 'Nice and Nicely Done'; there's a few good tracks there.
Stars: Awesome indie/electronic stuff, some really good songs. You should definitely listen to some of their stuff... there's also an album made by several other bands featuring covers of a CD (the 'remake' album has the exact same songs as the original, just different versions).
Voxtrot: Really Really Really good. Go listen to them. Personally I prefer their EP, which although has lower quality because it was essentially a demo track, all the songs are great.
The Weakerthans: They're a band that grew up in my home town, and my friend is related to them... They've got several CDs, of which get better chronologically imo. Take a listen maybe. Fact: I'm taking guitar lessons from the guy that taught their lead guitarist. ;p
Anyways, that's about all I have to reccommend for now.
