I own the 2-disc "Happiest Celebration on Earth" CD set from Walt Disney World, and I thought it was DEFINITELY worth the price of around $25. Here's what's on it:
DISC 1
1. "Remember When" LeAnn Rimes performs this song, which is the theme song for the Happiest Homecoming (Disneyland)/Celebration (everywhere else). It's very pretty; probably more relevant to Disneyland, where they play it after "Remember...Dreams Come True" (the fireworks) that to WDW, but since Disneyland is the park the celebration is for, I definitely support the song being on WDW's CD set.
2. "All Aboard" The loading call for the Walt Disney World Railroad. Short track, but special; it's a definite "sound of Walt Disney World" and is a good example of how the CD set really evokes the feelings of being in the parks.
3. "Welcome Medley" Music from a street performance where singers and dancers ride down Main Street, USA in a trolley and sing and dance to welcome them to the 'most magical place on Earth,' as they call Magic Kingdom in the song.
4. "The Tiki Tiki Tiki Room" The original version, as you can still hear at the Disneyland version of this attraction. A nice tribute track, since Tropical Serenade (WDW's Tiki Room, which I *believe* was a clone of the original from Disneyland) has now been 'updated' to the Enchanted Tiki Room: Under New Management and this song is no longer played in its entirety.
5. "Swisskapolka" The music you hear as you walk through the Swiss Family Treehouse.
6. "Yo Ho (A Pirate's Life for Me)" From the classic "Pirates of the Caribbean," of course. This isn't the ENTIRETY of the ride, but at over five and a half minutes, is lots more than just a quick cut of the pirate band singing the song. It's designed to be heard the way it would be as you go through the ride; condensed, but still very evocative. A highlight.
7. "Friend Like Me" Starts basically the same as the "Tiki Tiki Room" (though with the voice of Jerry Orbach as the French bird, Pierre), then is interrupted by Iago from Aladdin, who sings his own version of that film's Genie's big intro number about how the Tiki Room needs some modernization.
8. "Bear Band Serenade" One of the opening numbers from the Country Bear Jamboree show, in its entirety.
9. "Splash Mountain" Similar to Pirates, it doesn't run quite as long as the actual ride, but is still a very comprehensive (nearly 8 minutes; the ride runs 10) soundtrack to the ride. Very catchy songs, and even splashing sound effects at moments where the drops occur. Oddly, Brer Rabbit's solo version of Zip A Dee Doo Dah is BEFORE the ensemble version on the Zip A Dee Lady, whereas the reverse is the case on the ride itself. Still, excellent! The sounds of the splashes really add a lot to making you feel like you're there.
10. "Grim Grinning Ghosts" The famous theme from the Haunted Mansion...like Pirates and Splash, it's not ALL the sounds of the attraction, but more than just the singing bust scene. It has the entrance music and part of the Ghost Host's opening spiel, music from the ballroom scene, and the song with its lyrics as performed by not only the singing busts, but some of the other ghosts that you can hear singing along to the song in the cemetary. (The song is played in its entirety 3 times). The track ends with the voices singing the "If you would like to join our jamboree..." verse towards the end/exit area and Little Leota calling out "Hurry baaaaaaaack..."
11. "It's a Small World" Singing dolls...catchy melody bound to get stuck in your head...a 5 minute version that covers a few of the different languages that it goes through on the ride.
12. "The Many Adventures of Winnie the Pooh" Cute, cuddly, bouncy...pretty much the music as you hear it on the ride...possibly slightly shortened, I'm not sure exactly how long the whole ride is, but this is over 4 minutes and covers all the major scenes in the ride.
13. "Solo Pilot Blues" I haven't actually heard this one in the park, but I'd assume it would be by the Barnstormer in Toontown Fair. (It's listed as a Toontown Fair song and is sung by Goofy.) It's cute.
14. "The Best Time of Your Life" This song for a while was the replacement for "There's a Great Big Beautiful Tomorrow" at the Carousel of Progress. The corporate sponser suggested the song be changed because it emphasized that NOW is the best time and encouraged consumerism...they were worried people wouldn't buy things now if they thought that tomorrow would have something even better to offer. (True story, heard it from Disney historian Jim Korkis.) ...yeah, people wanted "Great Big Beautiful Tomorrow" back and they got it.
15. "Planetary Boogie" As performed by Sonny Eclipse, the AudioAnimatronic alien who performs in the dining area at Tomorrowland's Cosmic Ray's Starlight Cafe.
16. "There's a Great Big Beautiful Tomorrow." The song is sung through by several different performers on this track, which runs about two and a half minutes. I think that all of the recordings are from the CURRENT version of the attraction (the ending is, for sure), which is not the same as the ORIGINAL from the World's Fair/Disneyland, but it is still nice. The entire original version of the Carousel of Progress is on one of the CDs in the 6 CD Musical History of Disneyland box set. Check the Wonderland Music machine at Main Street Cinema, too, and see if there's a CD devoted just to that attraction. (That machine will burn legal copies of several out of print Disney CDs, some of which are soundtracks to attractions; it was $15.96 plus tax while I was on the CP if you would be interested!)
Now we leave Magic Kingdom and head to Epcot...the next few tracks are all 'extinct' EPCOT Center songs.
17. "EPCOT Entrance Medley" Futuristic-sounding music with "Energy, You Make the World Go 'Round" featured prominently. Not the same loop currently played at the entrance to Epcot, so this is a nice look at Disney history.

(All of these extinct EPCOT Center songs are, really.)
18. "Tomorrow's Child" Theme song of Spaceship Earth before the ride was refurbished/altered. Really lovely song.
19. "Energy, You Make the World Go 'Round"
20. "The Universe of Energy"
Both of those are from the old, pre-Ellen DeGeneres/Bill Nye version of Universe of Energy, which was...rather dry and dull, but did feature some nice catchy songs that live on even if they are no longer a part of the show.
21. "Test Track Medley" This is pretty much the music that you hear as you wait in line for Test Track...not really a ride known for its soundtrack, but it's still kind of cool to have the music on the CD. (This obviously isn't extinct, since the ride is still there.)
22. "It's Fun to Be Free" Back to Exctinct EPCOT. The theme song of the World of Motion pavilion, which was plowed to make room for Test Track. I like that this track and the one before it are next to each other on the CD.
23. "Listen to the Land" Another dearly departed EPCOT song...it used to be played on the boat ride in The Land pavilion, which was called "Listen to the Land." The ride was renamed "Living with the Land," the song went away. It's another really really catchy one, though, and it's nice that it lives on.
That's the end of CD 1; this is really long, so I'll do CD 2 in another post. Oh, and CD 1 ends up running a total of just over an hour and 17 minutes.