So in the interest of sharing, here is what I have learned with integrating Facebook to Drupal.
I've been using either of these modules:
Depending on the complexity you need.
For the first one (fbconnect), this is simply a way that someone can log into a site using their Facebook account. It's fine for a site where you just want to encourage user registration --- someone can log in using their Facebook account and then either connect their FB account with their user account on the website, or start a new user account on the website.
The second one (fb) has much more complexity and extended permissions -- for if you incorporate things like publishing to the FB stream, importing photos or information from the FB profile into the Drupal equivalent, or creating a FB application using Drupal.
I've found #1 to work in the majority of cases as most of our clients are not yet on the bleeding edge of facebook integration.
A few things to monitor:
The above-mentioned "projects" are basically "wrappers" that you must install as modules into your Drupal site (usually into pathtoinstallation/sites/all/modules/*) but you always have to get the current version of the Facebook SDK through whatever channel it's being distributed (e.g. git hub).
You must reference the FBML markup language in the "Head" of your page.tpl.php file, in order for the Facebook buttons to display.
You must sign up for a Facebook account, as well as set up a Facebook Application here:
--- from here you can get the Application ID and the Secret Code.
Finally, there is a difference, at least in terms of how Facebook understands your site, between www.mysite.com
and mysite.com. You must use .htaccess to specify which version you want, and then set up the Facebook Application accordingly.
I'm happy to talk more on this and show you sample versions of what we've done.