Tune Us In is a free online MP3 to ringtone converter. you can Upload any mp3 song, cut out the part you like and it will help you to convert it to a ringtone. Once the ringtone is ready you can either forward it to your mobile phone or download and save it on your computer. No sign-up. No cost. No limit on the number of ringones you can create.
Check out TuiConverter here
its very nicely designed site to operate with. it also very helpful to find new softwares.