As my 4-year recertification timeline was about to lapse, I had to go and pay $350 to recertify :) There was no other challenge, as I picked CCDE written for recertification, keeping in mind to take the practical test again this year. To my greatest surprise, the exam was almost the same it was in September 2007, when I took the beta version. Just this time the number of questions was 100 not 170 and they give you chance to review and navigate among the questions (just like it was in old CCIE Written). Apparently, the CCDE written test engine has never been updated the way that CCIE R&S Written was, with the new scoring model based on 1000 points. Since 2007 I spent considerable amount of time studying (back then I went unprepared, but still passed with 70 point) so the exam went disappointedly easy, as I haven't seen anything new that I didnt see in 2007. As usual, the main focus is on IP Routing with the addition of Tunneling techniques (MPLS, GRE, IPSec) along with QoS, Network Management and Network Security. You may find the very detailed blueprint here (though formatting is broken in a number of places):

http://www.cisco.com/web/learning/le3/ccde/ccde_exam_information.html

The books I found most helpful to prepare were:

- Definitive MPLS Network Designs
- BGP Design and Implementation
- IS-IS: Deployment in IP Networks
- OSPF: Anatomy of an Internet Routing Protocol
- Optimum Routing Designs (you may mainly concentrate on IGP protocols and refer to the book above for BGP)
- EIGRP for IP: Basic Operation and Configuration
- Cisco IP Routing by Alex Zinin (for you hardcore routing fans)
- OSPF and ISIS: Choosing and IGP for Large Scale Network
- Layer 2 VPN Architectures
- Interconnections, 2nd edition: Bridges, Routers, Switches and Internetworking Protocols. (Just for fun reading and a lot of background information)
- IP Quality of Service by Srinivas Vegesna

The below one might be a good candidate for review the week before your exam. However, be aware of its condensed format and some technical inconsistencies:

- CCDE Quick Reference by Russ White and Mosaddaq Turabi.

Lastly, anyone preparing for the CCDE certification - even though the written test is easy, do not take it lightly as you'll need all the knowledge during the practical test. There are other challenges in the practical exam, but hopefully the plan I developed to deal with that will work for me - we'll see ;)