You can utilize mp3 players such as Winamp, iTunes or MusicMatch to convert your CD audio to mp3 format.
You can also take a look at programs such as dB Power Amp, Audiograbber or CDex, as these programs can convert your CD tracks into mp3 format. You may be able to convert non-mp3 audio files (WMA, RAM, etc) into mp3 using these programs.
How do I convert my iTunes files to MP3 on a Mac?
If you have your music/content which you want to broadcast in iTunes but they aren't the right format (MP3) you can convert a song to a different file format while keeping a copy of the original. For example, you can save a copy of an uncompressed song file such as AIFF or WAV to a compressed format like MP3, AAC, or Apple Lossless Encoder.
If you haven't imported some songs into iTunes yet, you can import and convert them at the same time. This will create a converted copy of the file in your iTunes Library based on your iTunes preferences. To convert all the songs in a folder or on a disk, hold down the Option key (Mac) or Shift key (Windows) and choose Advanced > Convert Import preference setting. The Import preference setting will match what you chose in step 3. iTunes will prompt you for the location of the folder or disk you want to import and convert. All the songs in the folder or on the disk will be converted.
Note: Some purchased songs are encoded using a protected AAC format that prevents them from being converted. iTunes Plus purchases are not protected and can be converted.
To convert a song's file format in iTunes version 7-10:
1) Open iTunes Preferences
2) Choose iTunes > Preferences.
3) Click the General button, then click the Importing Settings button in the second section of the window.
4) From the Import Using pop-up menu, choose the encoding format (MP3) that you want to convert the song to, then click OK to save the settings.
5) Select one or more songs in your library, then from the Advanced menu, choose Create MP3 version
To convert a song's file format in iTunes version 11+:
Most of the other options from the former Advanced menu are in other sub-menus on the File menu, with the exception of the CD import options which have been moved to their own options menu that appears on the CD import screen.
The option to convert media files can now be found under File > Create New Version.
Previous versions of iTunes display the audio conversion option (shown below), is based upon your default audio import format. The setting for this can still be found in the same place, by going into iTunes Preferences, and selecting Import Settings from the General tab.