For my 1Y0-A20 XenApp 6.5 administration exam I’ve used a lot of knowledge base articles and other resources besides the self paced online course (courtesy of my employer).
This is a great document which shows all ports used by all Citrix products. Not only useful for an exam but also for troubleshooting purposes.
Here are the most useful kb articles and other free online resources I used to prepare for this exam.
5. Profile management
6. Application streaming / profiles and launching
7. Access gateway / Web interface
8. Worker groups
9. Session sharing
10. Content redirection
11. Workspace control
12. Logon restrictions / reboot
13. Database options
14. Load evaluators
16. Speedscreen / image compression
18. Planning server functions