If you can't bear to be out of touch with your Facebook buddies for more than a few minutes then you might like to try out fim.
fim (Facebook Instant Messenger) is a tool that optimizes the Facebook Chat service for Windows Mobile devices. To set the program up, you need only insert your Facebook account details and fim will display a neat list of who is online along with each person's profile picture and current status.
Using fim to chat couldn't be easier. Just tap on the person you want to speak to and a chat window will appear where you can just start exchanging messages. Unfortunately, the chat features in fim are very thin on the ground (as is true of Facebook Chat itself), so don't expect anything fancy like emoticons, file sharing, or picture messaging.
Aside from instant messaging, fim also lets you access other areas of Facebook, such as Home, Notifications and, rather neatly, Phonebook, from where you can call people with a single click on their number. The presentation of Facebook in fim is rather clunky and doesn't really offer that much advantage over browsing the site in Internet Explorer.
fim does its job without any fuss, but if you want the best Facebook IM experience on your Pocket PC I'd recommend something like fring or Nimbuzz over this one.