Afternoons and Coffeespoons by Crash Test Dummies -- A band, perhaps known best for Mmmmm, and SuperMan song... but I love all the songs from their early albums. Of the albums available on iTMS, I'd recommend this song as a very catchy Crash Test Dummies song.
Landspeed Song by Tanya Donelly. Tanya was a member of Belly, Prior to that, Throwing Muses. She's been solo for a little while now. I find this song quite energetic. I recommend this whole album actually (Lovesong for Underdogs)
Why Can't I by Liz Phair. I can't say this song is necessarily my fav from the album... but is good and previews well. Liz Phair just released a new album this year, and I think it's worth listening to.
Warren Zevon -- "Dirty Life and Times." Probably my favorite song from his last album
The Sundays -- "When I'm Thinking About You." She's got such an awesome voice.
The Vines -- "Country Yard." I bought the album on a whim after hearing one song, and it's really growing on me...
the album Truelovewaits by christopher o'riley is just fabulous, whether you are a radiohead fan or not. i strongly recommend Let Down, Black Star, and Thinking About You. it's all good new age style piano solo. Marc Ribot -- "Aurora En Pekin"
If you want to know what Belly might sound like today if they had stayed together and spent the last 10 years playing in obscure clubs, listen to Cat Power's new album "You Are Free." My favorite track is Free.
Interpol is best known for the song PDA, but my favorite off "Turn On The Bright Lights" is NYC. News networks should have played in the background during the NY blackout crowd shots this August.
Finally, it's hard for me to pick out just one track from Damien Rice's great new album "O", but I'll go with Volcano. While you're there, buy the whole album.
Peter Gabriel -- "Growing Up"
I first heard this on Delta Air Radio, coming home from Geekfest DC 2003. It's funky, it's a bit dark, but it's Peter Gabriel.
Lamb -- "Lusty"
TripHop, killer beats, great vocals...gets me going!
Massive Attack -- "A Prayer for England"
Pretty much, this entire album is great. This track in particular has such a compelling, smoothness to it...moving & emotional.
Everything But the Girl -- "Wrong"
Most people are familiar with the track "Before Today," but this one is equally as good...smooth with a bit of dance appeal.
Hooverphonic -- "Out of Sight"
Her voice...the samples...the feelings that generate through me when I listen to this track...get this entire album.
For the classical fans: O Fortuna by Carl Orff; the overature to Carmina Burana, one of the most awesome pieces of choral glory ever written. Sadlly overused in advertising, but still great; Seraphim Classics - Bach: Favorite Organ Works; over an hour of fine Bach organ music for $6. Can't go wrong.
Speedy Marie by Frank Black
You're not done knowing what pop guitar rock is until you have this song. Preview doesn't fade out (weird).
You Were Right by Built to Spill
This song is in 3/3 (or is it 3/4? Waltz-like, anyway) and it borrows lines from famous songs and cliches. The preview is in a lower bitrate than 128, apparently. One of my favorite "alternative" bands that are signed to a major label.
Mesmerizing by Liz Phair
This is a far better Liz Phair album than the new one (which sounds like Avril), IMO. I went ahead and put a link for the whole album, which I actually bought at iTMS. The song "Mesmerizing" does not have explicit lyrics.
The Kruder & Dorfmeister Sessions: Gone (The Kruder & Dorfmeister Sessions) from This Film's Crap, Let's Slash the Seats
"The World's Spinning at 45 R.P.M." by Pizzicato Five
"Ceremony" by New Order
"Metal" by Gary Numan
"(I Got A) Catholic Block" by Sonic Youth
"Gloria" by Patti Smith
"Too Much Paranoias" by Devo
"The Fairest of the Seasons" by Nico
Some fun remixes:
Bjork: Big Time Sensuality (The Fluke Minimix) LINK
U2: Night and Day (Steel String Remix) (7 minutes long) LINK
Rob Zombie: Living Dead Girl (Subliminal Seduction Remix) LINK
Dinah Washington: Is You Is or Is You Ain't My Baby? (Rae and Christian Remix) from Verve Remixed LINK
And...
Orgy: Blue Monday (new Order cover) LINK
Moby: Soul to Love (iTunes exclusive) LINK
Tori Amos: China (The whole album's good too.) LINK
Primitive Radio Gods: Standing Outside a Broken Phone Booth with Money in my Hand LINK
Also... albums I've bought with a lot for the price:
Barenaked Ladies: Disc One - 19 songs (1 hour 13) for $9.99
U2: Rattle & Hum - 15 songs (1 hour 12) for $9.99
Vangelis: Spiral - 39 minutes for $4.95
I went through some of the songs in my iTunes and picked a few that are favourites currently in heavy rotation...
Pin by the Yeah Yeah Yeahs - Just a fantastic song for when I'm bouncing off the walls. We need more women like Karen O in music!!
Too Many People by the Pet Shop Boys - A fantastic classic. A great song for when I'm riding the metro to work.
I Love My Computer by Bad Religion - Need I say more?? 
parrothead all the way
Margaritaville- Jimmy Buffett You can pick which one is your favorite.
Like a Rolling Stone- Bob Dylan Come on. This has to be one of the all time greatest songs of all time.
Elegia by New Order
If you haven't seen the animated short "More" I suggest looking it up on the internet. Good luck with it, though, the only places I knew of that had it both removed it. Anyway, the song is played from start to finish during it and it works very well.
The World I Know by Collective Soul
Good song, but that may be somewhat personal, it brings back memories.
Tangled Up in Blue, and All Along the Watchtower, both by Bob Dylan. If you don't have any Dylan songs, get some. These are just the first two in my list of his stuff, but I like them both a lot.
A couple of quickies:
Jeff Buckley - New Year's Prayer
Rahzel - If Your Mother Only Knew
ok hmm.. ah yes first off:
Portishead - Dummy
This whole album is amazing, unfortunately song # 2 and 5 are currently missing from iTMS. Specificly i recommend checking out Mysterons, Numb, and Biscuit.
Beck - Sexx Laws
This song is hilarious in classic Beck nature. Great beat too.
Counting Crows - Mr Jones (Live)
This is an awesome live version. this whole live album is great too.
Jeff Buckley - Hallelujah
Great song! although i have a diff version than this live one on iTMS, but... i just bought this one, and its just as good if not better!
Sum 41 - Over My Head [Acoustic Version]
The Crystal Method - Keep Hope Alive
Sum 41 - The Hell Song
Rob Dougan - Furious Angels
Freddie Hubbard's Red Clay is a great energetic fusion tune. 12 minutes long, too, so you get your money's worth.
The Bad Plus, "Keep the Bugs Off Your Glass and the Bears Off Your Ass." Hard to describe. A unique jazz trio.
Karsh Kale - Liberation - the title track from Karsh's latest album. Good electronic music with an Indian vibe to it.
Ok, here are my choices, they are mostly pop punk, I would really love you guys to give a listen even if you don't buy any songs.
Lucky Boys Confusion- Hey Driver - great song off their new album which comes out next week.
M.E.S.T. - Paradise (122nd and Highland Street) great pop-punk band and a great single very catchy
another lucky boys song I can't resist these guys are great, from a town near mine and a few of the nicest rock guys i've ever met.
Lucky Boys Confusion-Fred Astaire
My favorite song at the moment...
Bigger Than My Body by John Mayer From his new album, Heavier Things. Great guitar, a nice relaxing song.
Learn To Live What You Are - ben folds
Baba O'Riley - The Who
Extraordinary - Liz Phair
Island In The Sun - Weezer
Comfort In Sound - Feeder
Where the Hood at? - DMX
Uncertain Smile, by The The
And for a classic, check out - "Night In Tunisia" by Charlie Parker
But they finally got some Galactic into the store. Only one album Vintage Reserve. Century City has always been one of my favs.
I would have to many to list... but a few would be:
"Other Side" by David Gray.
any album by David Gray actually. He is masterful.
"Primitive Notion" by New Order
"is this real" by LisaHall
"Swords" by Left Field
"Butterfly Caught" by massive attack.
any album by massive attack is a good one.
"Dam" by matthew ryan...
Who can forget this (Tubular Bells by Mike Oldfield) ...it still gives me chills.
My faves
KJ-52 - Dear Slim
KJ's letter to Eminem in the style of "Stan". Was such a hit that the song made it to TRL.
Caedmon's Call - Shifting Sand
Always loved it but since my friends got together and performed it recently, I love it even more.
DC Talk - Colored People
I tip my hat to the colorful arrangement 'cause I see the beauty of the tones of our skin.
Some things on the jazzy side:
Blue Bossa, a duet between the classicly-trained latin pianist Michel Camilo and the late conga player Mongo Santamaria. Unfortunately, iTMS doesn't have Camilo's best works yet ("Live at the Blue Note", recorded earlier this year, comes to mind).
West Side Story Suite as played by violinist Josh Bell. I dare you to try to find another enjoyable 19 minute song for a dollar.
La Fiesta, a epic, two piano, 22 minute bout between Chick Corea and Herbie Hancock.
Ben Folds' Speed Graphic EP, Ben Folds' Sunny 16 EP, because it's always fun to support an artist doing something different.