Some Contiki-based research papers have recently been published:      
The Announcement Layer: Beacon Coordination for the Sensornet Stack. Adam Dunkels, Luca Mottola, Nicolas Tsiftes, Fredrik Ă–sterlind, Joakim Eriksson, and Niclas Finne. In 
Proceedings of EWSN 2011.
This paper introduces a new layer in the low-power wireless  stack: the announcement layer. The announcement layer coordinates and  piggybacks beacon broadcasts to reduce both energy consumption and radio  congestion. The code is intended to be included in Contiki after the  2.5 release. The paper also presents the first performance results of  the ContikiMAC radio duty cycling mechanism. PowerPoint slides are also available.
ContikiRPL and TinyRPL: Happy Together. Jeonggil Ko, Joakim Eriksson, Nicolas Tsiftes, Stephen Dawson-Haggerty, Andreas Terzis, Adam Dunkels, and David Culler. In 
Proceedings of the IP+SN 2011 workshop.
This paper looks at low-power IPv6 interoperability from a  performance perspective. We run Contiki and TinyOS, both running IPv6  with RPL routing, in the Contiki simulation environment and find that  although both systems have a good performance on their own, the  performance in a combined network can be surprisingly low.
Leveraging IP for Sensor Network Deployment. Simon Duquennoy, Niclas Wirstom, Nicolas Tsiftes, and Adam Dunkels. In 
Proceedings of the IP+SN 2011 workshop. 
This paper studies how the protocols in the low-power IPv6  stack behave during network deployment. In particular, the paper looks  at software deployment and demonstrates that a simple mechanism in the  ContikiMAC low-power radio mechanism is able to significantly improve  throughput with a retained low power consumption.  
The Politecast Communcation Primtive for Low-Power Wireless. Marcus Lunden and Adam Dunkels. 
The ACM SIGCOMM Computer Communications Review, April 2011.
This paper argues that the traditional broadcast primitive  sometimes is overkill in low-power wireless networks and argues that  there is a need for a new communication primitive, called politecast. A  politecast transmission reaches only those neighbors that explicitly  listen for it. Politecast transmissions are intended for periodic, but  redundant, beacon transmissions.