Forum Attachments for BuddyPress plugin by _ck_, boonebgorges and cuny-academic-commons gives members the ability to upload attachments on their posts.
It’s a port of a plugin originally created for bbPress by ck. See the original plugin page here: http://bbpress.org/plugins/topic/bb-attachments/. ck is not supporting this plugin anymore.
Plugin homepage: http://teleogistic.net/code/buddypress/forum-attachments-for-buddypress