There is no RSS feed for LinkedIn groups, as they all require the viewer to be a LinkedIn member to join (at a minimum).
You could use the Groups API and the recommended PHP wrapper Simple-LinkedIn to get the recent posts from a given group, but the catch, as with all LinkedIn API integrations is thta the viewer must be authenticated against the API. SO on your custom page that shows recent discussion, the viewer would need to have authenticated against LinkedIn, and depending on the group permission, be a member of the group.

There is no RSS feed for LinkedIn groups, as they all require the viewer to be a LinkedIn member to join (at a minimum).
You could use the [Groups API][1] and the [recommended][2] PHP wrapper [Simple-LinkedIn][3] to get the recent posts from a given group, but the catch, as with all LinkedIn API integrations is thta the viewer must be authenticated against the API. SO on your custom page that shows recent discussion, the viewer would need to have authenticated against LinkedIn, and depending on the group permission, be a member of the group.

[1]: https://developer.linkedin.com/documents/groups-api [2]: https://developer.linkedin.com/documents/libraries-and-tools [3]: http://code.google.com/p/simple-linkedinphp/