OS X tools to export iTunes library to mp3

"iTunes itself can do that. I presume you ripped your songs without changing the import settings in preferences, and they got ripped as AAC, right? Just go to Preferences, Import Settings:

Set it to Import Using MP3 Encoder, and select the quality setting you want.

Now you can right-click a bunch of songs in your library, and select “Create MP3 Version” to convert them all.

This also affects any CDs you import from now on, so I’d suggest re-ripping them directly to MP3 instead of converting your existing files, to avoid any further loss of quality from converting from AAC to MP3."

"iTunes can do the conversion itself:

Select ""Preferences"" (this is under the iTunes menu on a Mac, under the File menu (I think) on Windows).
In the ""General"" tab, click ""Import Settings...""
From the ""Import Using"" selection list, choose ""MP3 encoder"" and click OK. Click OK again to exit Preferences.
Select the tracks you want to convert to mp3s.
From the ""Advanced"" menu, choose ""Create MP3 version"".
Create a Smart Playlist for which Kind equals MP3.
Select File->Library->Export Playlist.

That's pretty much it."