A Johnny Cash cover of the Beatles "In my Life" got me thinking about covers of famous songs done by other well-known artists. Are there any favorites out there?

Meh, never liked them... never liked improvisation in music anyway.

You might like this: http://www.youtube.com/watch?v=zDV0PMvhrB8 ... not an exact cover though, since Emma also provides the vocals for the original.

Excellent! She has an amazing voice, thanks for the link.

For The Beatles' "In my Life", I actually prefer Bette Midler's cover version.

Johnny Cash - Hurt (Nine Inch Nails cover).

Nick Cave and the Bad Seeds - Sleeping Annaleah.

Type O Negative did some amazing cover versions. These one in particular are excellent.

Cinnamon Girl by Neil Diamond
Summer Breeze by Seales and Croft.
and they did a great Beatles Medley (Day Tripper, If I Needed Someone and I Want You).

those later Johnny Cash ones like Hurt etc are intense! Its cool when they are just as well known as the originals or obscure they can be very intersteing.
http://www.youtube.com/watch?v=NSwRXaUbQzE
http://www.youtube.com/watch?v=-ALRLZQf42s
http://www.youtube.com/watch?v=cHgBnYIdSzA&feature=related Yes they're mostly all schmaltz exploiting one listen and worth only 1...like a well known song switched to a diff genre, yet some entire genres have this skill to be great at it like reggae for example.

improvisation lol,
http://www.youtube.com/watch?v=L5OhXFk6DzI

A Perfect Circle's cover of Imagine sends shills down my spine.

I prefer Richard Thompson's version of Time to Ring Some Changes... which is sort of a cover of his own song. He wrote it for the Albion Band (which he wasn't a member of at that point) and theirs was the first version recorded (although what I linked to is actually a live version). I'm not sure if Richard Thompson has ever actually done a studio version. I've read your post, re-read the first post, re-read your post and I still can't work out what you mean. o.0

EDIT: To clarify, what are you referring to when you talk about improvisation? Johnny Cash? The Beatles? Covers? I can't see how improvisation links to any of those things...

I have a few

I am the Walrus - Oasis over http://www.youtube.com/watch?v=98Z2vQDqpVw
Tobacco Road - Jefferson Airplane http://www.youtube.com/watch?v=9FyJ4FGfOVc

One of the most famous covers is House of the Risiing run by the Animals:
http://www.youtube.com/watch?v=ZxYGeTV6fCw

And finally, this would have been an epic cover but unfortunately only part of it was recorded for a movie:

Blue Skies - Brent Spiner aka Data (star Trek: Nemesis)
http://www.youtube.com/watch?v=RLEvqYLfupk

Making a cover = isn't that when a person sings / plays a song / track made by another person using guitar and/or similar instruments live?

No... covering is just playing someone else's song. :P It can be live or a studio recording. I've arranged, played and recorded a bunch of covers just for my own amusement and just because I like the song.

EDIT: It doesn't have anything to do with it being live or on a guitar. A cover can be any situation and any instrument. It's not necessarily covering whoever wrote the song though, more who it's associated with. I'm pretty sure Britney Spears didn't write any of her songs, but if I was to record one of them (god forbid) it'd be a Britney Spears cover rather than a cover of whoever wrote it.

Pretty much what I meant. I mostly see it done with guitars and pianos.

I don't like live music much. Barely actually, another reason why I'm into trance (everything needs to feel smooth and arranged intelligently). :p