BP Better Messages is a BuddyPress plugin that turns BP Messaging into a threaded instant messaging type communication tool. You can disable the requirement for a subject line and also enable name search and file attachments.
GR Dashboard notes, whilst not being specifically a BuddyPress plugin could be useful for membership sites with a few admin and moderators. This plugin allows you to add notes to the dashboard that will only be seen by members of specific roles. So for example it could be used to send a general note to all admin, and they’d see it as soon as they visited the dashboard.
LH Logged In Post Status is a WordPress plugin that adds a new post status of “Logged In” to the available status options in the Publish dialogue box. What this means is that posts can be published only to logged in users, which is an option that would enhance the privacy options available for post content.
BuddyPress Xprofile Custom Image Field is a plugin that adds an image selector to the range of profile fields available to BuddyPress. When installed, it allows for users to add images to their BuddyPress Extended Profile.