the answer is simple, you cannot download free music without doing it illegaly, i would've thought this was pretty obvious as artists need to make money.
also the answer to you "why are limewire,bearshare,kazaa etc. not illegal" well heres you answer.
these shareware programs are not promoting in anyway that you are to share copyrighted material, e.g. music free of charge, they are just ther so people can share uncopyrighted material, i.e. home photos, and when somebody does put something on them that is illegal then it is not this program companies fault, they are just providing a service of sharing, it is the sharers fault who shares illegally. its like a pub selling beer and not getting fined when somebody goes drink driving, its the pubs beer thats done the damage yet the drinker and driver is the law breaker, just as the downloaders/uploaders are when using shareware.
anyway the answer to you primary queery, the answer is there is no where legally for free music, apart from an interesting new marketing ploy whereby an artist releases a single on the internet hoping you like it and download more at a price or buy their album.
i read the first page only when posting this so i hope people have not pre-answered you questions.
EDIT: seen as how im in the mood ill use code as well, use a well known program for downloading music called lemonplug, hehe, its reliable in finding many-a-songs even the most remote of music, its free and you can download t.v. programs as well like lost etc. its slightly illegal but as long as you scan a download if its a program then you shud be fine, all music files are genuine.