Folks over at XDA-Developers have managed to extract and run Windows Marketplace for Windows Mobile 6.5 on Windows Mobile 6.0/6.1 devices! All you have to do is to download and install the .cab file discussed here which will then download an update for Windows Mobile to make it ready to use on Windows Mobile 6.0/6.1 devices. This .cab file fix will also work on cooked ROMs of the recently leaked builds of Windows Mobile 6.5 Build 230XX and 234XX branch.
If you have any one of the popular Windows Phone and want to try out something new, then check out the new ready to install cooked ROMs of Windows Mobile 6.5 Build 23409, which are now available for a variety of popular Windows Mobile based handsets listed below.