Hi Guys,
P3dO is for sure a unique tool for Carrara, I am providing Carrara support in P3dO since October 2009.
In short: Carrara and HDR thumbnails viewing is free, Carrara files References list in InDepth tree is free too. You have to register to edit thumbnails and get the thumbnailed view of a scene References.

As GKDantas said I am working on Video tutorials, but at the moment you can visit the Carrara features page at Senosoft.com which tells all about Carrara in P3dO:
http://www.senosoft.com/carrara_file_manager.php

It is short and both a description page and a Tutorial. Looking at the pictures should be enough. Well, I hope. If you have any question I will be glad to answer.

Yarp
www.senosoft.com

Yarp - author of P3DO Organizer for Poser