Vitamin Strings Quartet. They cover all kinds of stuff from classic rock, to modern pop, to hip-hop... but with a string quartet. They have thousands and thousands of songs. The album page on their website has hundreds of albums. It would be impossible to listen to it all, but odds are they've covered some of your favorite songs. Here's one. Actually found this looking for wedding music, my fiancee is going to walk to this...

http://www.youtube.com/watch?v=QrZsU7x1aFk

Also, I got into Kavinsky last week, that was my most recent find. Doesn't have a ton of music out there, but he makes some great electronic music. Has a very 80s feel to everything he does, and it's intentional because one of his album names is "1986". He did the main title track for the movie Drive. I saw movie recently, and thought it was a catchy tune, and discovered him as a result. I love the 80s electronic feel to his music... can't get enough of it.

All of his songs revolve around a character that he created, and the character's Ferrari. So the character is a zombie who died in 1986, and all of his songs are about him coming back to life, still dressed as if he was in the 80s, still driving his Ferrari Testarossa, and generally being an 80s badass zombie. Just figured I'd add this, because it kind of explains his videos with the Ferrari, the letter jacket, and the 80s vibe. I've been digging it, but the guy doesn't have enough stuff out!

Kavinsky - Protovision:

http://www.youtube.com/watch?v=41_svUt5_e0

Kavinsky - Nightcall (The Drive title track):

http://www.youtube.com/watch?v=MV_3Dpw-BRY

Lot of his others are good stuff too. Been listening to it at work all morning so far.