emusic.com is running a promo where you get 50 free MP3 downloads.
http://emusic.com/ray
You have to register for the service, but you can cancel immediately after downloading your songs. I did it and was a member for about 10 minutes! No DRM on the files and I received no spam afterwards. The selection is broad, but many specific titles I searched were not there.
Also, I don't know if any of you use
http://yourmusic.com. All CD's are $5.99 with free shipping (they do charge sales tax). You have to sign up for their subscription service where they ship you one CD a month (this is how I ration my music purchses!). Box sets are at the same rate (for example a 3-CD box set would be $17.97). They have a broad collection and many of the titles I want are there (many are not, though). They have a limited number of dual discs with DVD included for the same $5.99. I've been using this service for about a year and a half and am pleased with it.