While the Blackberry has had a native application for Facebook for awhile now, it seems Windows Mobile and even Palm has joined the fold.
Windows Mobile and Palm devices now both have a native application for Facebook. For the Palm this application supports the Centro, Treo 755p, and Treo 680. If you have the 700p model, it might work as well if you select the 755p version. You can check out more for the Palm version here
As for Windows Mobile, they have a application call FriendMobilzer that does the trick. You can check that out here