Napter is now offering free access to their two million+ song library, and its all legal. Now the catch, you can only listen to a song five times, then if you want to listen to it more you have to buy it.
Its really not a bad deal, personally there's not a lot songs out there that I enjoy that much that I would want to buy them. Although, with the way they have there service setup there is a much better chance that I would buy the songs that I really like from them. Another great feature about Napster is that you don't have to download and install any special software to listen to the music (unlike other music services).
To take advantage of the offer you have to register with the site. What this means is that you have to choose a user name, enter your email address, and select a password.