ERDaudio is a Web interface for playing audio files. It uses the MPD audio server and should work anywhere MPD and mpc can run.
Nuvola Player runs web interface of cloud music service in its own window and provides integration with a Linux desktop (system tray, Ubuntu sound menu, dock menu and notifications). Currently supported services are Google Music, Grooveshark, Hype Machine and 8tracks.
Weboob is a project that provides several applications (console or graphical) to interact with a lot of Web sites. There are more than 13 supported Web sites and 15 applications to view bank accounts, drag on dating websites, search and play videos, display the weather, read news, show train timelines, get torrents on trackers, and perform other useful tasks.