Chorus is an add-on for XBMC that lets you remotely manage, build playlists, queue up videos, organise your library and do just about anything you want with your media centre. And you can do it all from the comfort of a browser window on another device.
Chorus looks great, if you can't tell from the screenshot above (there are more screenshots here), and the web interface is easy to use. You can control your media centre from a browser window (as long as you know the IP or dynamic hostname of your XBMC machine). You can use Chorus to control what it does on the big screen, or stream music and video directly through your web browser. You also get support to play your local media files on your XBMC machine or stream music you have on your laptop up to the big screen instead of the other way around.
You can even build playlists through Chorus so the music won't stop, or you can set up a whole season of a show you're watching so you can enjoy it without having to go back to the menu and select the next file to play. Chorus is free and available in the default XBMC repository, but you can also grab it from GitHub at the link below.