Was one of the first apps I downloaded and love it. Ringdroid allows you to take songs from your playlist and turn them into customized Ringtones. The thing that I love about this app over other ringtone apps is that it allows you to take sections of songs and use them as your ringtone. Other ringtone apps I've used only allow you to use the beginning of songs.
The app is simple to use. You can cut out sections of songs as short as a second or as long as the entire song and turn it into a ringtone. I use it to cut out my favorite parts of songs for ringtones. You can do as many songs as you like. Once you have clipped a section of a song you have the option of turning it into a ringtone, notification or alarm sound. The droid incredible makes it easy to add the customized songs and notifications to your contacts.
Basically it is a fun, cool and simple app to use.