For music see the Supernatural.tv listing for complete lists of music from the show. I recommend iTunes for quick purchasing- see my iMixes for current listings of what is available on iTunes. For additional tracks- check out your favorite mp3 download sites. Certain titles will require purchase of actual cds. AC/DC's library is not available to download at this time.
For video- check out Amazon for the best consistent prices on Season 1 DVDS. I recommend iTunes for Season 2- get a season pass and watch without commercials on your video iPod and PC. I bought a $20 cable at radioshack that attaches my iPod to my DVD recorder so I can make back up DVDS to play on my DVD players until Season 2 is available on commercial DVDs.
Additionally the official CW website now has streaming videos for some of the current season episodes so you can view with your own high speed connection on your PC- no downloads available but nice clean video. http://video.cwtv.com/
CW on Amazon Unboxed
Buy subscriptions or single episodes of your favorite shows on Amazon.com that you can rent or keep. These are US downloads for now- check your country Amazon site for non-US unbox deliveries.