BP Activity Share is a plugin that allows users to share the activity updates of others, similar to how this can be done on Facebook.
BuddyPress Activity Social Share is a simple plugin that adds various social share options to BuddyPress Actvity items.
Social Graph Protocol BuddyPress YR is a plugin that aims to improve the information presented to Facebook when BuddyPress pages are shared onto this social media platform, it allows you to edit Meta tags that will be passed to Facebook when your WordPress and BuddyPress Activity pages are shared. This means that you have greater control over how your site is presented.