The web version of Xbox Live Marketplace is now (almost) at your disposal, giving you a back up option for redeeming Microsoft Points, purchasing games and searching content available for the Xbox 360. Technically, it's up, but there's not much to see or do at this point, as a good portion of the web Marketplace responds with the message "this marketplace catalogue is currently unavailable."
Eventually, we presume it will be a good option for surfing the available games, demos and movies available for the Xbox 360, as well as managing your account, but not quite yet. Interested users should be aware that the web Marketplace requires Microsoft's Silverlight plug-in, lest they walk away from the site disappointed or raging at the existence of Microsoft's Silverlight plug-in.
Xbox Live Marketplace [Xbox.com]