A few weeks ago Amazon.com added a new perk to its Amazon Prime premium service.  In addition to free video streaming and free delivery options, the service now includes free access to a large music library in the style of competiting services such as Spotify and Sony's Music Unlimited.  While the current selection has its share of rock, pop, rap, country, and other popular genres, it's easy to miss that the service also has a handful of video game soundtracks available for free streaming.  Famous game soundtracks such as Portal 2, Batman: Arkham City, The Last of Us, Bastion, and Mass Effect 3 are available for on-demand listening.  I've dug deep into the catalog and picked out the currently available relevant music for your enjoyment.  Not every track from every album is free to stream (the Video Games Live albums on the list only have a few choice tracks available, but thankfully the Castlevania medley is one of them), but there's enough here to keep your ears busy for no extra charge beyond Prime membership.  Enjoy!