XenServer and Creedence
The following are my own recommendations to run Scientific Linux in XenServer:
I recommend using XenServer 6.1 through any of the Alpha releases due to improvements with XenTools
I recommend using Scientific Linux 5 or Scientific Linux 6
The XenServer VM Template one will need to use will either be of CentOS 5 or CentOS 6: 32 or 64 bit depends on the release of Scientific Linux you will be using