Microsoft's just launched the Xbox Live Pipeline website, which is an online catalogue of Xbox Live Marketplace content for (potential?) Xbox 360 users. It's a lot easier to browse all the various content available from a web browser than from the 360, which points out some flaws in the XBLM design.
Although you can see most of the stuff available, you can't actually download or do anything with this information. The most you get is, well, a redirect to xbox.com and get more info on an item. It's a far cry from the Xbox Live Anywhere experience demoed to us at E3 where you can trigger downloads on your Xbox 360 from your phone or PC using Xbox Live Anywhere. We're still waiting for that.