Accuradio hear your choice of many varieties of music free, but with ads.
Bandcamp hear new indie music free, with opportunity to purchase from artist.
Bearshare hear and download free music in a variety of genres. Playlists for your mood.
Classical Music Online hear classical music. Search by genre, country, concert, or collective groups such as specific orchestras, ensembles, quartets, etc.
ClassicalConnect Search by instrument, performer, composer. Hear music, artist interviews, read liner notes, more.
Jamendo hear, download and share many sorts of indie music for free, at this site that works with Creative Commons.
Last.fm is a music discovery service that suggests new artists based on the music you listen to. Assorted genres, but best for pop, rock, and related mainstream genres.
Live 365 Listen free, but with ads. Online radio searchable by wide-ranging genres and sub-genres (example, within Folk, select from Contemporary Folk, New Acoustic, World Folk, Alternative Folk, Folk Rock, and Traditional Folk.)
Mixcloud Hear online music radio shows, mixes, or talk radio, follow your favorite disc jockeys, search by popular genres.
MP3 Grabber An online tool to get music and videos from YouTube and similar sites into mp3 format so you can put them on your portable device. No need to install plugins, software or register to use this free tool. You can search for the content you want using its search box.
Pandora music discovery with the Music Genome Project. Drop the name of one of your favorite songs, artists or genres into Pandora. It scans its world of analyzed music, new and old, well known and completely obscure - to find songs with interesting musical similarities to your choice. There are ads.
SoundCloud hear fresh music and spoken word podcasts. Follow what's trending now in genres including many kinds of music, science, storytelling, comedy, and more. Scroll through your choices by using the "category" box in the top right corner of the page. SoundCloud is a social sound platform where anyone can post and share.
Spotify sign up to hear music free, including many of the biggest, most popular artists and genres. Search by artist, album, genre, playlist, or label. Expect ads.