Pandora is a free to use anytime, you can listen to one of your favorite artists, composers, or the songs you like, and pandora can suggest you music that you may be very interested, I use pandora on my android phone and I pretty much enjoy it everywhere I go on my 3G/4G and Wi-Fi data.
You can make a free account by using your E-mail and password, and if you're sick of the advertisments on your phone or on the website, you can always upgrade your account on pandora.
I don't have much info that I can give you for now, I'm still using this currently, my friends suggested me to use it, and pretty much when I get bored from listening my music that I purchased, I use pandora to listen to my favorite band/composer such as Hans Zimmer, Green day, and Linkin park.
Discuss.