Hi,
Critical path is the longest path in a network diagram and this is more focused on tasks, where as Critical Chain is more focused on resources.In Critical Path we concentrate on tasks in terms of resource and time efficiencies, causing schedule risk and while in critical chain we stress on human resources on executing multiple tasks.

Regards,
Vishwanath

Here is one of our webinar recording where we had good discussion around critical path

http://www.youtube.com/watch?v=n5ZCJDWkS84