With Freegal, you can download (and permanently keep) up to 3 songs per week.
From the PPLC site:
Visit Freegal for thousands of recordings by your favorite artists. Log in to Freegal Music with your library card number and PIN and begin downloading! Current limits are set at three downloads per week. Your counter will set back to zero each week Monday morning. Then you can download three more tunes during the new week.You can also use the Freegal site on your computer & then transfer songs to your MP3 player or other mobile device.
If you have any questions/problems, please write us at firstname.lastname@example.org or give us a call. Remember, the default PIN # for your library account is the last 4 digits of the phone # that we have on record for your library account.
Scanning the QR code below with your smartphone will take you directly to our mobile site, or you can be automatically redirected if you visit our homepage on a mobile device. Then click on the "Databases" link to get the link for the Freegal app of your choice.