There are a number of Ringtone managers for Android, ranging from Free to $$$. Ringtone managers are all basically the same, they allow you to set individual ring tones for each contact. Since Android 1.5 this has been included with the Contact manager. What the built in manager doesn't provide is the ability to set MP3 ringtones.
My first introduction to Ringo was for Palm when I did a review for PA (link). At the time it was great. It brought a whole new world of ringtones to my Treo 650. It added individual ringtones to my contacts and gave me access to a library of great ringtones and MP3s. It also provided 'group' ringtones.
This brings me to Ringo Pro for Android... As soon as I received my G1 I started surfing the Market. As soon as Ringo appeared I quickly grabbed a license and started playing with it. Ringo comes in 2 flavors for Android Lite and Pro. Initially Lite wasn't available, and really the only difference is the access to MP3 ringtones.
My first impression of Ringo for Android was not good. I didn't find it as powerful as it was on my 650 and most of all it was missing group ringtones. One nice feature was the SMS/MMS integration, Ringo provides the ability to set different tones for messages as well. Also Ringo provides a nice pop-up feature for SMS alerts.
Overall, Ringo Pro for Android is a great app, but the are free apps that do just as well. And if you were hoping for the ability to set group ringtones like it does for every other platform, well it doesn't. So while I was happy to purchase license and support the team behind the app, I'll be sticking with the free app "RINGS EXTENDED". But make the decision yourself.
To give Ringo a try check out: http://ringomo.com/android.php or search for "Ringo" on Market.
If they ever figure out the group ringtone feature it will definitely return as my ringtone manager of choice.