Your iPhone or Windows Phone probably already notified you of the existence of an update for the Facebook client installed on your phone. If not, however, you should know that the iOS version has hit build 3.4.4 and the one for Windows Phone is already at 2.1.
Facebook 3.4.4 for Apple-phone users brings a couple of improvements (or reverts to be more specific): the Send button for Comments, Chat and Messages has been restored and so have the friend lists to the News Feed filter. There are also some bugfixes included an your client will hopefully crash less.
Facebook 2.1 for Windows Phone promises to fix the bug which prevented you from accessing your friends' picture albums. You can download both updates by following their respective application store links below or just tapping the update notifications on your phone.