Complete My Album
Apple has added a catchily titled new feature to iTunes, which allows you to buy single tracks and then if you decide you like the sound of an album you can use Complete My Album to only pay the difference. It remains valid for up to six months, but it currently allows you to do if for any previous purchase.
I just had a look and I don't think I need the rest of Whitney Houston's Greatest Hits.
29th Mar 2007 - Tumblr