I just typed in Eruption half speed, and it came up.
You can find all sorts of things on youtube like that.
Type in a song title, and some keywords
isolated track
isolate guitar
isolated guitar
a capella
There's all kinds of isolated vocals. the Police's Roxanne has cool vocals to begin with. Without music, the harmonies are really awesome.
Leona Lewis singing 'Keep Bleeding Love' a capella gives me goosebumps.
Steve Perry, Freddie Mercury, Paul Stanley. They're all there a capella, if you take the time to look for them.
Jake E. Lee's isolated guitar on Bark At The Moon is wayyyy more sloppy than it sounds when surrounded by the rest of the song.
I looked for maiden, but all I could find were isolated rhythm guitar, no lead solos. Bummer.