Oh la la la! Sign up for an lala account and create your own online playlist (which you can access from anywhere). You can then play any song or album once for free, purchase a web song for 10 cents (with unlimited online plays), or download the MP3 version for 79 cents.

I love the site for its networking element — you can connect with friends, find folks with similar musical tastes and gift songs. I find the catalog of available tunes incredibly comprehensive and the site easy to navigate.