There are several sites online that will produce some exceptional content for streaming your favorite mp3 or other audio files. The one that I personally like is Pandora. There are others that have a lot of value add or different ways of presenting the music, but it seems as though Pandora is one that has sign off from the record companies and is doing things the right way from a legal perspective.
There are plenty of ways online to download your tunes. Most of them strictly speaking are illegal meaning you don’t have the right to download the tunes that other people are posting. For instance, with the mp3 indir searches that anyone can do using Google, there are no shortage of places to download your tunes. You could even find mp3 ringtone download files as well.
To get legit, however, you need a site that has the rights to play these files online. There are traditional internet radio stations that can put their content out there on the web, but they don’t allow for the same level of interaction and although you may have a favorite station, it may be tough to get them to consistently play music you like.
Pandora is different in that regard. They leverage something called the Music Genome Project. This is a catalog of thousands of songs, possibly even millions (I don’t know the exact number). The catalog contains characteristics of songs including the vocal qualities, rhythm, beat styling, genre, artists, albums, etc. The project documents these characteristics then will begin to build a profile of what songs seem to match the qualities in the other songs you’ve told the site that you “like”. Pandora is not necessarily revolutionary in just that sense, but has introduced thousands of people to new music, new artists that they may not have found otherwise.
In this way, the site is a great place to go for your tunes.