I don’t often just endorse websites or software, but Finetune is a great example of where software is going. With a full-fledged music-player, playlist builder, and radio functionality online – they took it a step further and started providing air applications to play from your desktop. See finetune desktop
Additionally, they took the initiative to build a wii-compatible version of the site. This means all your content is playable through your sound-system via the wii internet browser and your television. This is no small challenge, since their framework is flash 9, and the wii opera-browser is only flash 7.