RSS Feed and Reader works both ways:
ACP > Modules > Listing > RSS Feed and Reader
Each module's feed is at yoursite.com/feed/(module address), for example:
yoursite.com/feed/audio yoursite.com/feed/blog yoursite.com/feed/gallery
To change what a module's feed contains, put a template named (module)_item_rss.tpl in your skin, such as skins/(your skin)/jrAudio_item_rss.tpl.
{jrFeed_list name="your_feed_name"}Shows the latest items of an RSS feed.
Feeds are cached, so a new post on the other site can take a while to appear.