From Electric Pocket:
Ringo Pro for Android is a great way to truly personalize your Android phone. Use any MP3 as a ringtone and set individual tones for each of your contacts and groups. It really powers up your SMS notifications too, set a different tone for each contact's messages, and control LED colors, pop-up notifications. This application is packed full of customization options, so you can configure your incoming calls and SMS alerts exactly how you want them.
What's new in this version:
Version 1.3.7 fixed a tone picker issue on Android 1.5.