This week I've passed EX300.
Most of my study material came from Nightshade's book and Michael Jang's book for RHEL 6. I did do some googling when I thought that some thing weren't clear.Be careful- both books have mistakes (see multiple ssl vhosts in M Jang book)
I think the exam is much harder than EX200 and time is shorter so you have to be quick. Not all the objectives were touched. We were 5 in the classroom. One guy had time to solve everything and check some of the objectives but not all.
ADVICE: REBOOT AT LEAST ONCE. WE HAD A GUY WHO SOLVED EVERYTHING AND 20 MINUTES EARLIER BUT WHEN THE COMPUTER REBOOTED HIS COMPUTER DIDNT BOOT ANYMORE-> FAIL.
I think I'll go for the SUSE certification now (I live in EUROPE and SUSE is pretty common here).
I also sugest this guide -is good for a quick recap
RHCE: My study guide « João Ubaldo Blog
I will post in the next few days the labs I've done in the next few days(except those in the books).
Good luck guys on your exams