Graph from DoubleClick Performics showing major online holiday season traffic increases peaking on Mondays after Black Friday each year.
I cited this graph in an article I wrote on Preparing Websites for Black Friday and Cyber Monday.
About this graph, DoubleClick Performics says: "Here's how the seasonal sales patterns have looked for the last couple of years across our client base. Each year's data is lined up from Thanksgiving through Christmas, which falls a different number of days out each year, but is always the nadir of the season. The first gray bar is offline retail's so-called "Black Friday." The remaining bars are the four cyber-mondays. This season we'll have a fifth to take into account in budgeting."