If you are in the US (or can fake it), then you can get a digital copy of the Guardians of the Galaxy Soundtrack, aka "Awesome Mix Vol 1" for free! Just head to the Play Store and click on the "free" button.
And according to Android Authority (where I read about this to begin with), the Canadian Google Play Store is offering it for $0.99 (I would assume that's in Canadian dollars), which isn't quite free but pretty close, an entire album for what is normally the price of just one song.
So go and get it, even if you already bought the CD because why not?
And even though this was mentioned on an Android site, that doesn't mean you iPhone users can't make use of this. Just "purchase" the album on the Google Play website from any PC/Mac, then download the (mp3 format) songs and put them into your iTunes account. Same for Windows Phone but you can probably just put it directly onto your phone.