The RemoteApp and Desktop Connection Management service, which is part of the RD Connection Broker role service, is a new publishing feature in Windows Server 2008 R2. By default, the following three plug-ins are provided in the service:

• LegacyTS plug-in: Aggregates RemoteApp programs from Remote Desktop Session Host servers.
• VMFarm plug-in: Aggregates virtual desktop pools.
• MyDesktop plug-in: Provides the user with the assigned personal domain desktop.

All three plug-ins provide only RDP files, in the following scenarios:

• RDP files for RemoteApp programs
• RDP files for virtual desktops in virtual desktop pools
• RDP files for per-user assigned virtual desktops

In order to provide RDP or non-RDP files in any scenario other than the ones described above, you can write a plug-in to provide the list of resources, register it with the RemoteApp and Desktop Connection Management service, and display the resources in RD Web Access. For example, if you want to serve several different files (for example, some hand-crafted RDP files and some .osd (app-v) files that are on a physical drive on the machine running the RemoteApp and Desktop Connection Management service), you can write a simple plug-in that will aggregate the files from the location and pass them on to the service, which will then pass them on to RD Web Access. As a result, users will be able to access these files via the web page.

Source: http://blogs.msdn.com/rds/archive/2009/11/11/remoteapp-and-desktop-connection-management-extensibility-for-provisioning-apps-via-rd-web-access.aspx