Welcome to the Apple Community.
The Apple TV only works with iTunes, it can only share content from an iTunes library, it has it's own features which include iTunes rentals, netflix, Flickr, youtube etc but non of the sources you mention.
You may be aware of Airplay, which can stream additional content from apps and websites from an iPad or iPhone to an apple TV, however not all apps and websites are video enabled. There are many that are but a few developers haven't gotten around to doing it yet and a few possibly don't want to. My guess is the sources you mention aren't video enabled but can't be sure because I'm in the UK.
There is 3rd party software which can stream video from websites on your mac to the Apple TV, but the one's I've seen don't work very well and there are none I can recommend.
That's a realy nice discussion. Taking advantage of it, i'm wondering if there is a solution to show the content of a application (not video) from my computer into the TV using a Apple TV, Airport express, ...?
My intention is show the content of Last.fm application (with song information) while I'm playing a playlist.
Thank you in advance.