Here's a brief one I use. I'd love to hear how you people do it. Not perhaps in order, but a useful list for some hopefully.
1. Build template using semantic mark-up with CSS/XHTML
2. Validate with W3C for valid code
3. Verify on major browsers
4. Remove style sheets and view if it makes sense
5. Get people involved and note their process/difficulties around the site
6. Use CynthiaSays
7. Broken links?
8. Use correct DOCTYPE?
9. Well-structured mark-up
I guess this could cover Usability to a certain extent, so please contribute if you have further suggestions