www dot mobile17 dot com
Best site i've used before!! Just upload the song from your computer files, input what time you want tone to start at and how many seconds to go for, max is 45 i believe.
The only issue you will come across is the waiting line, it's free, but you are in a queue based on how many people are uploading and transferring. The best time.. Mornings for sure. never wait more than 20-30 minutes. Or just do it before bed and by the time you wake up, your song will be waiting!