Here is a fairly vague question for a SitePoint forum; but, I see no way around it.
I am wondering if a certain type of application already exists...if there is already something similar to what I am about to describe that I have just not seen before (not being familiar with social apps). My new site will be promoting a type of pledge, or "challenge", and it might help if users saw that their friends had "signed on" to the pledge. I would like to provide a simple way for site visitors to connect with one another.
Scenario: You have visited the site and have "signed on" to the challenge. Then, you send you pass an invitation to a friend...to check out the site (email, Facebook comment, etc.). If they decide to accept "The Challenge", they should be able to find your name...to be able to designate that affiliation or association when they "sign on".
If possible, I would rather that users not be required to have "accounts", to avoid requiring formal "registration". Yet, I want Sally to be able to see that her friend Joe has signed on, and let Sally look to see all of her "pledges".
I would look for examples or tutorials if I knew what to look for. Does this remind you of any sort of PHP application or social networking tool?