Converting this into a MP3 is a simple, but long process. Different encoders encode at different speeds and in some cases the resulting MP3 has a different quality. I use BladeEnc, because it was the first program I tried and the result always sounds good to me. Normally, encoding a wav into a mp3 is as simple as running the encoder with the wav's filename as the only argument. There are often other switches that set other details about the mp3, however, they normally do not effect the sound.
Some bands release songs for free download from their official web pages.
For example, the Beastie Boys recorded a live concert a few months ago and released three of the songs for free download in MP3 format. Also, other MP3 specific sites may be worth checking for MP3s, but most I have seen only have links to other sites, or search engines, which take you to other sites. Every time I check what MP3s they have, they only seem to have the same 4 songs. I could not find a link to an archive, so I assume they only offer the 4 songs. More Sites There are many sites on the internet with or about MP3s.