There are alternatives but they're all useless compared with the digitalpoint co-op because they don't give weight for traffic/impressions so you end up with your links on loads of "dead" sites that have page rank just 'cos they are expired domains. Examples are linkvault and receivelinks. Also tnx.net is a paid alternative which is even more useless.
I would say tnx.net but I have used it and I was not very satisfied with them some things to consider if you join them http://make-money-from.blogspot.com/2008/06/tnx-not-as-good-as-advertised.html if things have changed please follow up and let us know