It is unfortunate that we do not have an official Facebook app management for Windows Mobile, but there are ways to access Facebook on your mobile device. For those who want something more full-featured mobile version of Facebook (via m.facebook.com) when you go on your mobile browser, but do not want the full to load, you can access the iPhone version of Facebook, which developed such web application.
I prefer a portal for the iPhone because it does not look like all curled up to fit the display column. Instead, it has a tab at the top to jump around different parts of Facebook.
You can visit the portal by typing iphone.facebook.com into your mobile browser. Facebook mobile version can be accessed via m.facebook.com.