It was announced today that Microsoft cloud services see the light of day under the name of Windows Azure. It is basically Microsoft-hosted scalable on-demand hosting environment that looked (based on a keynote and few sessions) like a well thought-out, serious attempt to approach cloud computing. Financial approach was not disclosed yet, so it remains to be seen how attractive it will look.
You can get further info at http://azure.com as well as a download of the various SDKs which let you play with the services locally. Registration for live preview of hosted services puts you on a waiting list though.