There is an excellent article in the Journal of Athletic Training on concussions in sports. The article is a consensus statement from the 3rd International Conference on Concussion in Sport held in Zurich in November of 2008. The article reviews the evaluation, treatment, and return to play guidelines following a concussion in a very detailed but to the point manner.
The article also concludes with the inclusion of the SCAT2 (Sport Concussion Assessment Tool 2) that is recommended for use. The tool looks great and is something that I am going to implement in my athletes.
Best part of the Journal of Athletic Training is that the article is free to download (I have no idea how long it will be free):
Download now > Consensus Statement on Concussions in Sport