Though it's portion of one of my offerings that were compensated, I've decided to discuss this checklist. A couple of disclaimers: First, I really don't claim this list is special or extensive. Jakob Nielsen has an excellent 113-point checklist for example, Homepage Usability, in his e-book. That is just my way of arranging what I feel is important while attempting to keep it manageable. Second, my usage of terms may differ from yours. I use "usability" in a really broad sense, and my use of "accessibility" is not really industry-standard. Do not like it? Write your own checklist ;) Finally, an advance warning that this post is quite lengthy.
The list is split into 4 roughly equal sections, (I) Accessibility, (II) Id, (III) Navigation, and (IV) Content. I'll rationalize and explain all of line things and the sections below, but you could download the checklist as a simple, 1-page PDF.
I try to keep it easy with 3 fundamental ratings: (1) Green Check = Good/Move, (2) Red Check = Needs work, but no disaster, (3) Red X = Negative/Fail. Not allpoints are necessarily applicable to all or any sites.
Company landing page