Yammer site with features, mobile use, admin, and activation info. Trial is free, then you have to pay to use along with paying for office integration.
Free forum and message board platform that allows you to customize the look so it matches your website. They have an example of how they have integrated a forum into a website. Downside to free service are ads on the forum or message board page, but paid service eliminates that.
Can't find the date on this but Quertime lists 15 of the most widely used web forum platforms that we might want to explore. It does list BuddyPress as well. phpBB looks interesting, as does zetaboards, and maybe PunBB.