Jeff Beck
Try visiting this thread. Be sure to click on USCDiver’s link as well. Your life will never be the same.
Tortoise , as mentioned before. or many of the bands on thrill jockey records.
also, the nobody or kruder & dorfmeister remix albums are mainly instrumental, but im not sure they qualify as rock, even they bump like mofos.
also try drum and bass strip to the bone by sly, robbie & howie B .pure instrumental genius i reckon
Cruise Control by the Dixie Dregs. (The Dregs never had a vocalist, BTW).
Atom Heart Mother by Pink Floyd
In Memory of Elizabeth Reed and Mountain Jam, of course.
Glad by Traffic
Blind Eye by Wishbone Ash. This was a very odd song – it originally had lyrics, but for the single version, the lyrics were erased from the record (you can actually hear them very faintly if you cranked it up), turning it into an instrumental.
Ain’t Gwine to Whistle Dixie Any Mo’ by Taj Mahal
I have a mix tape of mostly 60s rock instrumentals. On it, other than ones that already have been mentioned, are:
Gold & Silver - Quicksilver*
Flute Thing - Blues Project
Embryonic Journey - Jefferson Airplane
Sunny Side of Heaven - Traffic
La Fuente del Ritmo - Santana
East St. Louis Toodle-oo - Steely Dan
Harvey’s Song - Harvey Brooks
Abaddon’s Bolero - Emerson, Lake & Palmer
Not exactly rock, but from that era and good tunes:
Percolations - Gong
Icarus - Paul Winter Consort
It has some Allman Brothers too, of course. Never was anyone to touch them when it came to instrumentals.
*Quicksilver, especially after they added the incredible Nicky Hopkins, did a whole slew of great instrumentals. I think there are a couple of every album. They are greatly underappreciated for a 60s San Francisco band.
Looked at two lines at once. Sunny Side of Heaven is by Fleetwood Mac.
Earl, the correct title is “Christmas Eve Sarajevo” but TSO’s music whips all types of ass.
“Hocus Pocus” by Gary Hoey is pretty hot, along with Satriani and Eric Johnson’s stuff which was mentioned above.
For a harder edge, try “Call of Ktulu” or “Orion” by Metallica.
Also, there were two songs on the CD for the original Carmageddon PC game, but I’ve never been able to track down the artists or titles (they’re in my mp3 collection as “Metal Instrumental 1” and “Metal Instrumental 2” - creativity was on low that day).
Edward, The Mad Shirt Grinder is another great instrumental by Quicksilver
Metallica-Orion
Metallica w/ SF Symphony- Call of the Ktulu (S&M version)
and I really like Satriani’s entire Surfing with the Alien album
Classical Gas by Mason Williams
and many many Hawaiian Slack Key artists such as Gabby Pahinui and Makana. These guys are way dif but both terrific. Jazz, rock , hawaiian guitar all in one. Maybe not your typical rock and roll but still awesome.
Hot Rats by Frank Zappa.
I should say that Hot Rats is the album title, not a song title.
To add to the Metallica suggestions, To Live is to Die from the …And Justice For All album.
I also second the mention of SRV’s Little Wing.
Ommadawn by Mike Oldfield. In that much-loved category, “Lone tortured genius determines to simultaneously silence critics and stun fans by giving full rein to his impassioned muse while demonstrating utter technical mastery of his chosen musical domain…”, (pause for breath) not much comes close.
Interesting side note. In my younger days I remember one or two women, with perfectly normal healthy curiosity, asking me what the male orgasm actually feels like. There is no finer illustrative answer than to play the concluding section of Side 1 of Ommadawn, and invite the female listener to pay particular attention to the final lead guitar workout. That’s what it feels like.
Another vote for Hot Rats – a fine, fine album. Another mostly instrumental Zappa album is Burn Weeny Sandwich. It’s most excellent, too.
ELP’s version Pictures at an Exhibition is great. The Nutrocker is pretty darn cool at the end.
How 'bout the Dixie Dregs. Been years since I’ve listened to 'em, but I recall them as terrific,
Actually, I have a Classical Gas with Mason Williams and Mannheim Steamroller; haven’t heard the Mason Williams-only album.
I’ll second GSYBE and add the Cancer Conspiracy
What, no one mentioned any Rush instrumentals yet? Do I have to do all the work around here? 
YYZ by the aforementioned promising new Canadian rock formation is easily my favourite instrumental of all time. Such skill! There’s a few other ones that kick ass. Leave that thing alone comes to mind.
And for complete symphonic hysteria, nothing beats Soundchaser by Yes.
Also, I can pretty much list all instrumentals by Savatage here.
I’ve always liked Tusk by Fleetwood Mac.
And this may be stretching the definition of “instrumental” a bit, but many songs by Boston feature amazing guitar work interspersed with a Wurlitzer organ – particularly Walk On.
The list is mind-boggling long (especially if you follow the links to the older threads and read those too). A ton of good stuff.
I’m posting only to relate this… I had a bit of a Twilight Zone moment when reading the thread from 2001 that includes an incredible list provided by Zenster. There was a poster who said something to the effect of “thanks… I’m going to be busy on Napster tonight.” Napster. Those were the days. ::fond smile of rememberance:: (not that I’m advocating illegal downloading of course.)