For some reason, songs in my itunes library are listed twice. Note: It is the exact same song just referenced twice, so removing one of the songs will keep one reference in the library but delete the song efficiently making the remaining song just a dead link.
this is similar to other superuser questions but not exactly.
Open iTunes and click on "View" and "Show Duplicates."
More /additional info:
In the menu bar, go to File > Library > Organize Library...
Check both Consolidate files and Upgrade to iTunes Media organization. 
Give your computer some time to process this, depending on how many items you have in your library.
It should now be solved. You're done.
Hope it works for you!
Might want to use this project to remove the duplicate files. Note the zip file contains the sources as well as binaries, the binaries are in iTunesCOMSample\iTunesCOMSample\bin\Release\ folder.
Press the Alt or Option key (for Mac OS X), or Shift (for Windows) -> View -> Show Exact Duplicate Items to display duplicates as this is normally a more useful selection. You need to manually select all but one of each group to remove. Sorting the list by Date Added may make it easier to select the appropriate tracks, however this works best when performed immediately after the dupes have been created. If you have multiple entries in iTunes connected to the same file on the hard drive, then don't send to the trash...
http://www.iphone-mac.com/find-delete-duplicate-items-in-itunes-library.html
This is a slight variation on KronoS above but I might suggest the following as a last resort:
This is assuming that you have previously allowed iTunes to organize your Music such that you have a well formed iTunes music tree (i.e. on a Mac, ~/Music/iTunes/...).
Go into ~/Music/iTunes and delete the following files:
iTunes Music Library.xmliTunes Library Genius.itdbiTunes Library Extras.itdbiTunes Library*.db or * Music Library * files in that directory which look to be backups.At this point you should have got rid of all the extra linking which is causing all your problems.
Once this is complete - you can try the following:
File > Add to Library and select ~/Music/iTunes/iTunes Media/ This should reimport all your music with only a single entry per file.
WARNING: This method will kill off all your podcast subscriptions, playlists and possibly album art and should only be used as a last resort.
Have you tried uninstalling and then reinstalling itunes? Also a selection of organize my itunes and then cancelling that operation may cause the duplicates to arise.
Just use the native iTunes duplicate track remover.
You can also follow these instructions in order to remove your duplicate tracks from your iTunes library:
