The Marketplace for Windows Phone 7 opened up in earnest just over a week ago and there are already something like 450+ apps with plans to get over 1,000 certified and in the Marketplace in time for US launch on November 8th. I recommend you check out the App a Day site to see what apps are appearing on a daily basis. I have purchased a few apps and am trying out several others thanks to the Microsoft policy that all priced apps are available to try out for free.
Here is a list of the apps I have loaded on the HTC Surround or Samsung Focus:
I show most of these apps in the video embedded below so you can see the quality of the apps and how many take on the look and feel of Windows Phone 7.
I also have the following games loaded up:
I see there are now titles like Earthworm Jim, Monopoly, and Tetris. I also see that the Xbox LIVE Extras utility launched very early this morning. I placed it on both test devices and see that you get some cool Avatar functionality with this, including the ability to fully customize your avatar right from your device, view your achievements, see your friends status, and send messages (for Gold members only).