An important update to Windows Marketplace was pushed out and it brings some useful new features. The ability to install apps on the memory card was probably the most requested of them - it deals with the common problem of not being able to install more than several apps because you've run out of internal storage.
The World View option in the Windows Marketplace lets you choose to view apps available for other countries - useful for when the app you want is not available for your area. Speaking of countries, the Marketplace has expanded into Russia, which means Russian users will be able to purchase apps and Russian developers can sign up to post their own applications.
The fees for submitting free apps in different markets have been removed and several restrictions have been lifted. VoIP over the data network is now allowed (unless the carrier specifically forbids it).
"Deep linking" is another new feature that came with the Windows Marketplace update. It lets developers create links from web pages that bring you straight to the purchase page of a given app. Applications already installed on the device can sport similar links, which will facilitate purchasing of the premium versions of free apps.