For new music, I really only listen to Top 100 type stuff, and like you said, you're already familiar with it. I tend to listen to older stuff like Jewel, Jann Arden, Cranberries, Alanis, Jennifer Nettle's FIRST band Soul Miner's Daughter (Sacred and Profane is a great album), Colbie Calliet, Ingrid Michaelson, you get the drift!

(wow, I listen to a lot of chicks!)

Mumford and Sons - Sigh No More. I can't get enough of 'em!

Adele is getting more popular but I like her shes got a killer voice and Natalia Kills is good for some more up beat sexier stuff Mirrors and wonderland are my fav. Don't know if they are up your alley

I'm not going to recommend music. I'm going to recommend services to help you find music.

One - pandora. For iOS, Android or the computer. Create a station based on your fav song or band and see similar.

Two - iTunes Genius will recommends music based on your list. If you already use it, just open the sidebar.

Three - Any sites like these link link / link

The combination of these methods have really helped me to expand my musical horizons!

I'm in love with a few less-well known artists I think you should check out -- Levi Weaver, Vienna Teng, and Susan Enan.

Have you heard anything by Foster the People ( try the song Pumped Up Kicks) or TV on the Radio?

I am terrible at classifying music, so I apologize if what I say below isn't quite what you expected. According to iTunes, everything I've listed below is "alternative," but I feel like they're all quite different. Here are some of my faves:

Folk
1]The Decemberists ~ there's an audio player on the far left: link
^^I love their rock opera album, Hazards of Love, and their story-form album, The Crane Wife, most of all.

2] The Swell Season/Frames/Glen Hansard ~ A Youtube Playlist link
^^I heard Glen and Marketa in the movie Once and have been in love with their music since then.

3] Mumford and Sons

4] Jump Little Children: JLC was the best! But they no longer play. Here's a Youtube playlist: link

4b] Jay Clifford: While JLC is dead, the lead singer Jay is still performing solo. Youtube playlist: link


Rock
1] The New Pornographers (with Neko Case) ~ link

2] Civil Twilight ~ link

3] Editors ~ there official site is currently down, but you can listen on Myspace: link

4] Block Party ~ link


Epic
1] MUSE ~ they deserve their own category in my heart ~ link

Also, my office plays Radio Paradise (link) and I have discovered a lot of new bands that way. It's a free "eclectic" radio station, and that adjective really says it all: They play old and new tunes from across every continent and every genre.

Slayer, soulfly, and kittie. My favorite Kittie song is cut throat. Soulfly is one of the bands that most people would like since they do variety of music, the band itself is heavy but the do songs with reggae, chorus singers, and other kinds of bands. They really are very good band songs to check out would be moses, fly high, and Jumpdafuckup. Slayer is heavy but still very good bad my favorite song is disciple, other songs would be bloodline, raining blood, and eyes of the insane. I like heavy stuff! Even if you do not I still recommend checking out soulfly you maybe surprised. These are not new either though they do have recent released music.