I need users to be able to log in via other internet services such as facebook etc. After they have logged in, they need to be able to fill out a form including various things, including one specific point: an embed code for youtube, soundcloud etc. I need to accept a payment before this information is systematically posted on the site. I also need a way for the people logged in with other internet services to interact in different ways. Whats the best way to go about doing this, readymade script, modified open source script, or fully custom site. For the most part, I don't want to enlist the services of people I cannot meet face to face. I don't want to give up the concept of the site too much but I want to give enough info so I can get adequate help. Any insight would be appreciated.