Here is a list of five very good Citrix resources that are available if you want to sharpen your Citrix skills:
Citrix E-Docs – This is the official online documentation for all Citrix products, provided by Citrix. You will find tons of answers there. It is a branch of the well-known Citrix support site, which is also provided by Citrix and where most Citrix public CTX articles are located
Brian Madden – One of the best Citrix resources on the web; Very educative and informative. Highly recommended
XenAppTraining – Also very informative and has some great free videos for you to look. You might need to register to watch the videos. I particularly like this Windows 2008 R2 configuration video: Win2008R2 Configuration . It gives you some good tips (time: 17min)
CtxAdminTools – Great variety of tools to make the Citrix and Microsoft Admin’s life easier. The author, Guillermo Musumeci is a Windows Infrastructure Architect with a “passion for designing, building, deploying and supporting enterprise architectures using Microsoft, Citrix and VMware producs” (from his About page )
CitrixExperience – Offers Free study guides for a lot of the Citrix Exams
Here are some free study guides for the Citrix exams.
Enjoy it!