This site will let you download certain tracks for free. Here you'll find find a few contemporary Spanish songs of famous Latin music artists (see Resources).
This website requires a username and password, so you'll need to set up an account to download songs (see Resources).
Once on the homepage, click the link labeled "Jibaricua Jukejoint." This link will take you to MIDIs and MP3s of classic Puerto Rican folf songs and alguinaldos (Puerto Rican Christmas carols). (See Resources.)
This website allows you to download Spanish music tracks with ease, but you will have to register first.
MTV.com teamed up with Rhapsody.com to bring the latest tracks to you. There are plenty of Spanish tracks to choose from here (see Resources).
This website has a nice listing of popular Latin tracks and more obscure world music Latin genres.