Whats a good music downloading site that is free, easy to use, legal, and easy to transfer to itunes?

im helping my cousin transfer music to her ipod. so i wnat a site that is easy to use and easy to understand, its legal so i dont get into problems, free, and the music is easy to transfer to itunes so i could then transfer to the ipod. like limewire except people keep saying its ellegal and stuff so i dont know about that one.