I still run across some bargain sets from Amazon MP3, and while some of the collections like ’50 Best Classics’ are always easy to find, some other gems surface here or there. All of these selections fall under the category “what do I have to lose?” since they may not be the top performances out there, but if you do not have these works and want to listen to them for next to nothing, well, WDIHTL? I cannot vouch for some of these recordings, many I just happen to run across and would buy if I did not already have the work. Perfect too for background listening or to have a copy of some works on your iPod / phone, etc. without ripping a cd. Most are around $1 per album unless noted below.
Debussy: Piano Classics [Over 5 hours and really good playing]
Mozart: Magic Flute – Beecham from 1937 [Old recording from 78s, but still a great rendition once you get used to the mono sound]