I know there are a couple of threads that come close to this, but not with answers that I have been able to use. On another multisite I used a plugin called something like WP MU Sitewide Tags. This created a blog that called in all the posts from all the blogs and posted them to the main site. These could then be displayed by category. But this plugin is a bit out of date and doesn't work with buddypress
What I want to do on an arts community install is to display on the main site any posts that members put up on their sites about new work, exhibitions, workshops etc. These will be default categories in all the sites.
From what i have seen this looks to require a cocktail solution, but am unsure if there is a way to get the mix right.