How can I get the IDs (or links) of a Facebook user's friends? Any app for that? His/her friends are visible to everyone. I can get his/her friends IDs manually but it takes long time.
A good start is : http://developers.facebook.com/
Just head for the documentation and in the API for user you will find it returns:
friends : The user's friends (Available to everyone on Facebook)
--> An array of JSON objects containing friend id and name fields
For example see: https://stackoverflow.com/questions/3340271