There have been a lot of albums that raised money for charity and the Warchild "Help!" album was a major flagship, produced in next to no time and almost every song on it being an absolute gem , but like Band Aid , some artists saw it as a way of promoting themselves or not putting on much effort because people would buy it and it's for charity.
The bad has included Ronan Keating murdering "In The Ghetto" and a completely soulless "Knockin On Heaven's Door" by Avril Lavigne but gems include "House of The Rising Sun" by Muse , "I Heard It Through The Grapevine" by The Kaiser Chiefs "Ghost Town" by The Prodigy, "Vietnam" by New Order and a lot more.
These albums serve a purpose and are worth exploring because you end up with some unusual and exciting covers, and some interesting original music and remixes.
Most of these albums don't seem to be available for download so you will have to grab yourself a copy , but I will leave you with "The Magnificent" by The One World Orchestra (which was really The KLF) from the "Help" album which is definitely worth buying.