With your library card number and Freegal's free downloadable music service you have access to about 15 million songs. Once you download the songs, they're yours to keep.
Download Limit: 5 per week
Streaming Limit: 3 hours per day
Note that copyright laws apply. The participating music labels have authorized customers of libraries subscribing to Freegal to download copies of the music for personal use. Sharing the music file with others would likely violate copyright law.