A few years ago (~2008) I realized most of my hard-drive space was occupied by music files - more than 50% were music files! I decided to move all of my music onto an external drive, and delete almost all of my music on my computer. I kept a small amount of only my top favorite songs and artists. I decided I would just use YouTube as my media player since I would be almost always connected to the internet anyways.
Well it worked - I didn't need all that music on my computer. There was a huge benefit to using YouTube as a media player as well. All of my playlists and songs were now available on any computer with an internet connection! I could listen at home, at work, and even somewhere random I've never been before. Since that time even more sites have popped up offering an even better online media experience. Here is a list of them.
I'm sure you've heard of Youtube, but have you thought about using it as a music player?
The Good: You can make your own playlist and save it on your account. Almost any version of any song is available - including live versions!
The Bad: Not every song is available due to copyright infringement - and sometimes songs are removed after you add them to a playlist. Also, adding songs to a playlist isn't as quick as some of the other sites.
Less popular than Youtube, but probably the most well-known free internet radio site.
The Good: Creates a custom playlist with minimal effort from you, based on your initial search and rating of songs it plays.
The Bad: Less popular genres and styles of music seem to have a very small bank of songs for Pandora to choose from. You cannot choose what song plays next, and sometimes there are short commercials.
So good, it's hard to believe it's free.
The Good: Enormous database of songs to choose from. Can create your own custom playlist and pick any song to play at any time. Very nice interface to boot.
The Bad: Nothing really.
A lot like Pandora
The Good: Creates playlists for you based on your tastes.
The Bad: Not able to select the exact song you want to play. Ads interrupt playback occasionally.
Similar to GrooveShark but geared more towards sharing and social networking.
The Good: Can create your own custom playlist and pick any song to play at any time. Very nice interface and large database of songs as well.
The Bad: Nada.
All sites are great solutions for leaving your music at home. GrooveShark, Playlist, and YouTube seem the best overall since you can play any song you want at any time with no interruptions from ads. Jango and Pandora are great as well, especially for finding new artists you might not have heard of otherwise.