Facebook Connect, how to allow users to find and invite friends to your site?

I've read quite a bit of documentation, and it's all based ar开发者_开发知识库ound on setting up full blown Facebook integration on your site to the point where you're completely relying on Facebook.

All I want to know is 2 things:

1) How do I allow my users to find out which of their Facebook friends have already joined my site

2) And what's the easiest way to let them invite Facebook friends to the site?

The site that does it perfectly and exactly how I want to duplicate is Gowalla at http://gowalla.com/friends/find

Note: I've never used Facebook Connect, however I have an API key somewhere.

You need to become best buddies with the Facebook Developer Documentation, especially the web guide.

Where you can start is the Login With Faces plugin, although the Facepile could apply as well. But understand this: If you're not using Facebook to authenticate your users (i.e., using Facebook Connect*), these plugins will be worthless to you.

In terms of inviting people, there's not going to be a great way to do that. You can implement request forms through the XFBML ServerFbml tag, but that's really for inviting people to other Facebook entities, not your own site. There's the share button but that's not really the same thing as an invite.

**Note: It's actually no longer called Facebook Connect - they are slowly moving away from that moniker. They are moving to the terminology "single sign-on". However, the "Facebook Connect" name still pops up in many places.*