After you've installed Apollo, the first application that you should install is the Finetune Desktop, available from the Adobe Apollo Showcase page. Finetune is a social music application that is miles ahead of Pandora. I've had it running all morning, and the music that its suggested so far has been great, similar to the experience I've had with Pandora. However, Finetune Desktop shines because it will also read in my iTunes library, and provide links to playlists for those artists.

Finetune uses Flash Media Server for streaming music, and PHP as the backend for the server. The application makes a series of REST calls back to the server, which returns XML that is read by the client application. This architecture allows them to create versions for the web, desktop (using Apollo) and even the Nintendo Wii (Flash is everywhere!).

Ryan Stewart has more information about Finetune. This is definitely one of the early Apollo applications that you should check out.