Some interesting Apps available on Windows Phone 7 Marketplace. However, my favorites are still not ready for release as of this writing (17th October 2010).
My take on those interesting apps. BTW, I did not want to try out non-free apps unless there is a trial selection.
The app is free and I have try it. Very nice. It is able to recognize the songs that I played on another phone. And best of all, it is free.
It is a paid app. You can use the camera to take a pic or use an existing picture. Once taken or selected. There is a effects tab that you can click. Once done, you can see the various effects on the picture.
Twozaic is a paid app. I have not tried before but here is a video of how it works
This app is free from Microsoft. Basically, a handy converter.
There are many more but I feel that the above are worth mentioning.
Here are some up and coming ones.
Here is a look at how Twitter looks like on Windows Phone 7