VLC Media Player is a free, open-source audio and video player and converter for both Mac and Windows computers. It supports dozens of input and output formats, including audio files like WAVs and MP3s -- two of the most common audio formats among Internet and portable audio device users. Note that because WAV audio is of CD quality and MP3s are generally more compressed and contain less information, you may lose some quality during conversion.
Launch VLC Media Player. Click the "Media" tab in the top-left corner of the main screen and select the "Convert/Save" option to enter the Open Media window.
Click the "File" tab in the top-left of the Open Media window. Press the "Add..." button on the right side of the screen to enter a pop-up search window containing your computer's contents. Navigate to your WAV file and click "Open" to return to the Open Media screen.
Click the "Convert/Save" button at the bottom of the screen to enter the Convert screen. Press the "Browse" button to get to the Destination File field, and choose a save location for your converted MP3. Name your file, making sure to include the ".mp3" file extension. Press "Save" to return to the Convert window.
Click the "Profile" drop-down box and choose the "Audio - MP3" option. Press the "Start" button in the bottom-right corner of the window to begin the conversion.