I created an album with different artists to listen on my iPhone. To my horror all the songs showed up as separate albums. Cover flow showed up the same album art for each of the songs. I hated this!! The fix is pretty quick. You have to make sure of the following to make your songs show up as one album -

1. The Album name has to be the same for all the songs
2. The Album Artist name has to be the same for all the songs
3. All the songs should be set as a part of a compilation.

Here is how you do it . Select all the songs in itunes you want to show up as an album, then right click on one of  the chosen songs and click ‘get info’ -

1. Type in the Album Name and Album Artist
2. Under the options tab, make sure the ‘Part of A Compilation’ is checked and set to Yes.

That’s it… That will make sure the album shows up only once for the entire album