Website: http://www.pdhlibrary.com/
State approval: Click throughs provide a pre-approval letter from the state of Maryland
Fee Structure: At least one course identical to a course available on cedengineering.com ($72) is available here for $29 (just a coincidence that I saw it both places – I did not do a thorough check for all duplicate courses). I see courses as low as $5 per credit hour. Most are $10 per hour
Ease of use: Limited use of categories make sorting and searching more time consuming than it needs to be.
Course variety: Limited water related courses available, not easy to search for them.
Course materials: A lot of course materials are copyrighted 2014, appear to be prepared specifically for the course.
Course instructors: Most water courses appear to be prepared by the same instructor, but you have to click through each course to identify the instructor. I only did a spot check for this.
Course ratings: not provided
Course packages: no
Personal experience: I have not taken a course with this company.
Preview course material: Yes
It may be worth it to check individual courses on this site to see if they are cheaper than the equivalent course offered on another site.
PDH Compare 