Without a doubt, I get highest traffic on Monday and Tuesday mornings. I live in California, so I schedule my posts for 5AM so that they are up by 8AM on the east coast (most of my audience is in the US). I also started using Feedburner to allow people to subscribe to the blog via e-mail, and those go out by 9AM.
A lot of people don't get online much over the weekend and Monday AM is when they catch up on emails, feeds, etc.