Hello! Alright, so since I just figured this out, I thought I would share - Did you just get the new HTC Droid Incredible, and you would like to use one of the various "make-your-own-ringtone" websites so you can send and save on your new shiny toy like me? What you have to do is:
1. Make your ringtone (Duh) and send it to your phone via MMS
2. When you receive the file, DO NOT open it... Instead, press and hold a finger on just the message, not the file.
3. After holding your finger on there for about 4 seconds, a save option will pop up. Save the ringtone, and then you can set it as a ringtone under the "Music" option in your phone.
Sounds easy enough, but it was a total pain trying to figure it out. (I have been a loyal LG customer for 6 years, and HTC/Droid settings kinda threw me.
Take care, enjoy your new phone, and feel free to post other tips and tricks for HTC DI users. :)