Webtone is another of what I am sure will be hundreds of Windows Phone 7 ringtone apps.
This app is designed to help you import ringtones from the web to your Windows Phone by copying and pasting the URL from a website into the app.
The main weakness of the app is that it does not make it easy to find ringtones on the web that’s free to download, but a site like this http://www.kthankzbye.com/newuploads/Ringtones/MP3%20Ringtones/ is a good start.
Webtone is however free and can be downloaded from Marketplace here. The developer is also working on getting rid of the kinks and making the app more robust, which i hope in the future will include a built-in browser and suggested sites.