If you're not a fan of the preloaded ringtones on your cell phone,
You can install the Ringback Buddies application by searching for the word "ringback" on Facebook, and from there you can do a number of things. First, you can see what songs your friends like or want, purchase them as ringback tones, and then assign them to your friends so they hear the track when they call you. There's also a Top 10 list of popular tones and jukeboxes (a group of tones) that you can preview or buy.
While free to add the app to your Facebook page, individual ringback tones are available from Verizon Wireless for an annual fee of $1.99 while prices vary for premade jukeboxes. In addition, there's a 99-cent monthly subscription for customers using ringback tones.