Frank Zappa - Rollo - the 72 version with vocals
Frank Zappa - Solitude - a love song he wrote for Gail - there are portions floating around on rehearsal tapes - it seems Gail finds this song very personal and doesn't want to share it.
Sensational Alex Harvey Band - No Complaints Department - originally intended for the Rock Drill lp - Alex's song about his brother Les (who was electrocuted on stage, his manager who perished in a place crash and others)
Jimi Hendrix - Black Gold - they only known copy was on a cassette given to Mitch Mitchell - who knows if it still exists.
Beatles - Helter Skelter - the 20 plus minute version - have not seen that pop up anywhere.
George Harrison - Mo - a song written for Mo Ostin that was on a promotional disc - IMO one of his best tunes.
Rolling Stones - C--KSuckers Blues - Done sort of in protest to fill their contract - but a pretty good song.
Bette Midler - I Gave My Heart to the Junkman - rockin version from the HBO show that was bumped from the Live at Last lp

No Complaints Department
"I've seen stars disappear in a hurry, overdoses of satin and silk" - this refers to the death of Elvis Presley who died as a result of stardom and rich living.

"Some others who can't feed their children coz they don't have the money for milk" - a reference to Margaret Thatcher who, as Education Secretary, abolished free school milk to primary school children and became known as "Thatcher the milk snatcher."

"So my best friend died in a plane crash, my brother was killed on the stage, so don't be upset if I'm angry and seem in some kind of a rage" - refers to the death of Alex's manager and best friend Bill Fehilly, who was killed in a plane crash in 1976 in the Grampians. Also a reference to Alex's younger brother Leslie who was electrocuted onstage with Stone The Crows on 3 May 1972 at the Swansea Top Rank ballroom when he touched a live microphone.

"There is no complaints department, it's only up to you..." - the chorus means that there is no point complaining about bad things that happen in your life. It's up to you to deal with it yourself.

"I've got friends who are armed with magnums, they don't get their money from me, coz it never is no kind of pleasure to see somebody suffer you see" - a reference to Alex's minder/bodyguard John Miller, who once tried to capture Ronnie Biggs and bring him to justice.

"They took my old pal to the madhouse, in horror and fear and in pain, with surgery done in a hurry to do a transplant in his brain" - refers to former Soulband guitarist Robert Nimmo, who suffered for many years with psychological problems

I've said it before and I'll say it again--a Rolling Stones BBC comp.

Other than that...hard to say. So many of my old (and expensive) bootleg CD's are now obsolete. The full orchestral take of "Strawberry Fields Forever" has always fascinated me, although parts of the unused first half of the song have been heard in Beatle documentaries. There's also any number of excellent possible titles in Dylan's "Bootleg Series".

However, as a collector, these days I'm more preoccupied with material that's gone out of print, or has never been made officially available on compact disc, than with unreleased material.

Cuba Si, Nixon No - Simon & Garfunkel

I'd like that and a Pink Floyd BBC release. These are the two BBC biggies that are missing as far as I'm concerned.

Well, unreleased on album, at any rate...

"Rip And Destroy" from KISS Meets The Phantom.

Another vote for the Pink Floyd, the unreleased Syd Barrett material. I know we've all heard them anyway, but let's have real, official, master tape quality releases.

A legitimate release of the Get Back album as originally intended.

Similarly, the original double album configuration of Red Rose Speedway.

The studio and BBC recordings by Paul Rodgers' interim group Peace.

The Beatles - Every take & mix of every song they recorded. No edits, no snippets, no "fly-ins". The three I most want to hear are: "Carnival of Light", "Helter Skelter" (take 2) (the full 27-minute version), & "Etcetera".

Bowie, 1980 Floor show & the original (superior) television mix of the Ziggy concert film. They've officially released 2 mixes of it. The current one is much better than the original official one, but the TV mix still slays either. The original official mix was AWFUL; with Ronson's (out of tune) guitar all but removed from the mix, & very prominent overdubbed back up vocals.

The most recent generation boots on 1980 Floor show (1973 Midnight Special TV broadcast from Hammersmith) are so good, that other than hi-res we almost don't need an official one, but it would be nice to have.

Jimi Hendrix - Generation Club 1968
Pennebaker has the original footage.

CSNY - the '74 studio album they were working on when the wheels came off.

buffalo springfield - stampede

neil young - toast

hendrix/stills - ?? - does this even exist?

Is the audio pro quality? I'd like to see that also if so!

Led Zeppelin - Swansong
Bits and pieces of it has floated around, but I don't know if the complete work as Page envisioned it has ever leaked out. Still have my fingers crossed that a "definitive" version of it will be released on the upcoming Physical Graffiti box.

Opeth - 2 Damnation era tracks
Do these even exist? The early press releases for Opeth's Damnation record said it had 10 songs. When it was released it was 7 songs + a hidden track. There was much speculation that 10 songs were indeed recorded and 2 were left off in a last minute decision. If I ever meet Akerfeldt the first question I'd ask him if there are any additional Damnation tracks that they left off the album.

Judas Priest - original Twin Turbo material that resurfaced on Ram It Down
Most Priest fans know that the 2nd album of Turbo material either was redone for Ram It Down or became bonus tracks on the remasters. But it sounds like some of stuff that was redone for Ram It Down was significantly different in demo form from the Turbo sessions (example, Ram It Down was Run Me Down and had a much faster tempo when it was released). I would love to see the original demo versions of Run Me Down, Monsters of Rock, etc get a release.

Prince
To many of these to even count. I bet there are 50+ songs that were mentioned on early track listings of albums or were on albums that never got released that have never seen the light of day...probably dozens haven't even been bootlegged. Just to name three, let's start with the Purple Rain era since there is supposed to be a deluxe version issued in the near future : Wednesday, Father's Song and Electric Intercourse.

Now that you mention it, I vaguely remember talk years ago of a Purple Rain era cd with all unreleased songs that never came out.