I am checking the documentation for Facebook,dailymotion graph api and soundcloud api, but I cannot find the list of the channels or users, a particular user is following.
Are there apis for the same?
Each company uses a different API, so you cannot apply the same methods to all APIs. For each API, you have to look into the documentation to find the right calls to make.
I can tell you about dailymotion API: in this API, you have to be careful that what are referred to as "channels" are the different categories, will the users are called "users". You can use the "following" connection in the "user" object. The query to make is a GET to /user/USER_ID/following The documentation for this connection is at http://www.dailymotion.com/doc/api/obj-user.html#obj-user-cnx-following