Oh, I need to add Drove All Night by Cyndi Lauper. Probably the finest thing she’s ever done.
Also American Dreaming* by Dead Can Dance.
Two different songs for two kinds of sex. (There are more, of course, but these popped to mind.)
For long, slow, spiritual lovemaking, you’ve got Pink Floyd’s “Great Gig in the Sky.”
For fast-and-nasty grab-your-partner’s-hair fucking, you’ve got Frankie Goes to Hollywood’s “Relax.”
Those pretty much say it all, for me.
Don’t go dissing Fleetwood Mac. I hate it when people sneer at a band just because they were insanely popular.
I’d have to nominate their “Landslide” as a song that’s damned sexy, not so much for the lyrics but because Stevie Nicks’ voice is saying “Take me now!” all the way through it.
And there’s Lucinda Williams’ “Right in Time” from Car Wheels on a Gravel Road.
Just remembered a couple;
Crazy on You - Heart (ooh, baby)
Wanna Make Love to You - Eric Clapton
Ana Stasia - Prince
I’m So Excited and Slow Hand - The Pointer Sisters
Lightning Crashes - Live
While My Guitar Gently Weeps - The Beatles
Leather and Lace - Stevie Nicks & Don Henley
And a second vote for Don’t Let Go by En Vogue
Kiss You All Over–Exile
Wicked Game–Chris Isaak
Don’t Touch Me There by the Tubes
Hey, Pretty by Poe
Great stuff here. I envision a CD burning soon.
For myself, already mentioned: Kiss by Prince and I Want Your Sex by George Michael.
I guess it depends upon what you mean by pure sex. I tend to focus more on the singer than the song. When I was between wives, just about anything by Bonnie Raitt from her “Nick of Time” and the follow-up album was enough to inspire the most desperate longings and cravings. She sounded like a woman opening herself up to me. Now, Wynonna and Mary Chapin Carpenter seems to be doing it to me lately. I’m just a slut for women with the right voice. 
My shortlist:
“Caress Me Down” by Sublime
“Go All the Way” by the Raspberries
“Hot Cherie” by Hardline
sugar high- coyote shivers
that’s my bubblegum teenage sex song baby!
hold on, i’m coming- sam&dave
heheheh…old soul says it best.
best sex album in my possession happens to be “Neither Am I” by a very obscure irish group called BellX1.
Volcano;
“don’t hold yourself like that,
you’ll hurt your knees
i kiss your mouth and back,
is that all you need”
and Face:
“how i choose bruise loose win sin bin tease please
better have her on her knees
play pray rock feel kneel dream.
how i choose to scream.
shout wake sleep need to touch her deep. change rearrange.
fate wait weight kiss or taste the place.
and make weather in my face.”
being the best songs.
sexy songs though are generally songs that just happen to be playing while you have sex, you can never listen to them again with a straight face!
I love Jewel. In a very wholesome way, mind you. My Jewel favorites are Jupiter and Morning Song. I think I have a lust reflex for her voice.
At the Dark End of the Street is the same song that was covered by the Committments (and lots of other people). James Carr recorded the first version. The Clarence Carter version is sublimely ridiculous – maybe I shouldn’t have included it. Then again…
“Cream” and “Get Off” by The Artist Once Again Known As Prince.
Patty
At Last – Etta James
Oooo laaaaa laaaa 
I’ll second (or third) the people who said Let’s Get It On by Marvin Gaye.
I’ll add Between the Sheets and For the Love of You by The Isley Brothers. Also, the original Giving Him Something He Can Feel by Aretha Franklin*.
*the En Vogue version is pretty good, too.
“Baby It’s You” by Smith
I’ll add Last Night by Az Yet and Freak Me by Silk to my list.
I would like to add to my list:
Do You Feel Loved? by U2
“Close to Me” - The Cure
[Robert Smith’s heavy breathing … oh my]
“Trip Like I Do” & “High Roller” - The Crystal Method
“Get Off” by Bad Religion - don’t ask me why, just seems oh so appropriate.
Oh, and for the humor factor, “My Vagina” by NOFX. Gotta love silly punk songs about getting a sex change.
I forgot about “Comin’ Back” by The Crystal Method.
But now that I think about it, might as well just nominate the whole damn album [“Vegas”], it’s all sex as far as I’m concerned.
Another vote for 60 MINUTE MAN-1953?-BILLY WARD & THE DOMINIOS
UNCHAINED MELODY–RIGHTEOUS BROS.(BOBBY HATFIELD)
A LITTLE BIT MORE–DR. HOOK
GREASED LIGHTENING—GREASE-SOUNDTRACK
Right now my number one with a bullet is on the Maxinquoye album by Tricky. There are many good ones on this CD. But the sexiest, in my opinion, is Overcome, (but Pumpkin, Aftermath, and Suffocated Love are also pretty good). I feel certain that this entire CD makes the Baby Jesus cry.
Also, I’ve got to mention:
Rough Sex by Lords of Acid
Crash by Dave Matthews Band
Natural One by Folk Implosion
Trigger Hippie by Morcheeba
A Girl Like You by Edwyn Collins
Take My Breath Away by Berlin
I Have The Touch by Peter Gabriel
Feel Like Makin’ Love by Bad Company
Perhaps, Perhaps, Perhaps by Doris Day. If you’ve seen Strictly Ballroom, you know why.
Already mentioned:
Feelin’ Love by Paula Cole. Ohhhhh, yesssss.
Justify My Love by Madonna
Closer by NIN
You Can Leave Your Hat On by Joe Cocker
Need You Tonight by INXS
Wicked Game by Chris Isaak
*Pour Some Sugar on Me * by Def Leppard. I’m just glad I didn’t have to be the first to mention this.
And I’m going to be looking up that song jarbabyj mentioned!!!