Now, the WP7 Marketplace occupied with ringtones apps, but maybe you want some free.
If you want to grab the free ringtones for your Windows Phone 7 such as for Nokia Lumia 800, you can download it freely with Myxer. Myxer is a really good-looking app with popular variants for Android and iOS and a pretty decent-sized collection of free tones.
As you visit the homepage, the most downloaded ringtones will be displayed. For example, if you use the app today, you’ll be greeted by lots of ringtones related to Halloween. Although a price is displayed ($0.00) for each tone, but that seems to be just a formality for now, as every ringtone we came across was free. The app allows you to preview any ringtone before downloading it.
You can search the app by going into the bottom menu and hitting search. But if you are not looking for anything in particular and just want a catchy ringtone for your WP7, you may browse through the categories presented by the app. In said section, you will find tones based on a variety of criteria like genre and popularity.
The app is free and so are the ringtones present in it (for now). Link to its Web Marketplace page is provided below.