Ari's Planet

Xining train schedule
http://cnvol.com/station-9/en-2571.htm

Xining agent recommended on LPTT forums
http://tibetanconnections.com/

Let's just hope signs in China are more readable than this web site: http://zt.tibet.cn/tibetzt/faq/1/2.htm

Tibet train schedule and information
http://www.seat61.com/China.htm

Government website with train schedule
http://www.gov.cn/english/special/2006-06/29/content_322568.htm