I've just added an itunes link for most every song except the Grateful Dead, which I am currently working on. Now you can buy the song or the album of the tab you are working on if you don't already own it. In most cases, I've found a direct match, but some artists are not added into itunes yet, or the particular song of that artist has not been added in. In those cases, I just get as close as I can.
I also have made the link to the artist who wrote the song, which may not necessarily match the tabs. I will be fixing this up as time goes on (I do believe I can make playlists that incoroporate more than one song).
So, download itunes if you haven't already and fill in the gaps in your collection.