Affiliationally WP is a Wordpress plugin for managing Affiliates (=friends’ sites) for fansites from within WordPress. Affiliate Categories and Affiliates are added through the WordPress panel and displayed with shortcodes in posts or pages. Affiliationally WP comes with the following features:

• import Categories, Affiliates and Link Buttons from the Affiliationally php script
• 4 different image sizes for every affiliate
• lots of displaying options
• widget
• apply form with akismet and additional spam protection
• notification emails (application and approval)
• overview in the dashboard, indicator for unapproved affiliates
• update function included
• use on all your “owned” fansites

You can find detailed instructions over here. Affiliationally WP has not been tested on WP multisite.