oof, didn't realize Pere Lebrun had beaten me to it with 'Little Johnny Jewel' – he did post the studio version however, so at least that creates a little compare & contrast
'LJJ' is unusual in that the song begins with a solo. They almost always come a couple of minutes in at least. Can't think of many other noteworthy examples, although 'Cortez the Killer' is stunning:
Plenty of other Neil Young solos worth mentioning; I've always liked the intensity of 'Southern Man', where he sounds as if he's grinding the solo into the face of the song. Or the song into the face of the solo. (Skip to solo.)
Most solos describe an arc, or an ascent don't they? A movement that builds in intensity from circular water-testing towards some kind of epiphanic moment - see Blissblog discussion of 'Marquee Moon' here. I think the 70s killed off a certain kind of solo which was more of a textural block, a series of small explosive detonations: moments where the solo doesn't sound like an attempt to escape the gravity of the song but burn a hole through it... like The Rolling Stones' It's All Over Now (skip to solo) or The Kink's You Got Me (skip to solo). Didn't Jimmy Page actually play the solo on 'YGM'? Dom nominates the Page solo from 'Ten Years After' here (why so English Dom, why not solos of distinction?). I would go for 'Heartbreaker'. One thing I especially enjoy about 'Heartbreaker' is it's studded with little errors (2m25s), moments where Page's finger can't quite keep up. But he's left them in (skip to solo).
Jazz flute interlude... Sonny Sharrock led a double life, paying the bills for his free/radical output by playing in flute snooze merchant Herbie Mann's band. Although it was Mann's vanity imprint that put out Black Woman, so u da Mann, Herbie. There are lots of anecdotes about Sharrock being allowed one Sharrockout a night on their supper-club dinner jazz tours, I remember reading one about a gig in a marina, all people in evening dresses lounging on their yachts. As Sharrock ripped out his wailing sheets of sound, the marina quietly drifted into a state of emptiness. You can hear him doing it to 'Hold On I'm Comin' from 5m30s ish here, although for the full impact it's worth listening to the preceding minutes of standard issue smooth funk.
Folk backwater. Carl mentions solos in Pentangle. I remember lovely examples on When I Get Home, and Sally Free and Easy – nothing on Youtube though & can't double check the vinyl till later. I think John Renbourn played all the electric in Pentangle. Jansch really hated the electric and had a thing about Pentangle as a respite from taking star turns. He did play electric in a one-off slightly disastrous gig at a St John's Wood pub backing an old blues singer (will have to look up the name), I've often wondered if there's a bootleg anywhere.
One more classic rock slash folk throwback before I post about Back to the Future and the solo AP (After Punk)... Buffalo Springfield's 'Bluebird' has an acoustic guitar solo, a definite rarity. I love it because it sounds so genuinely improvised and off the cuff, but also because Stills plays it so hard against the grain, against the instrument's type. He punches out this almost slap-bass, super muscular sound.
skip to solo
One more just because it popped into my head: Bob Quine's skincrawling solo on Lou Reed's 'Waves of Fear', here.